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Background: Salmonella, an important foodborne pathogen, was estimated to be responsible for 95.1 million cases and 50,771 deaths worldwide. Sixteen serovars were responsible for approximately 80% of Salmonella infections in humans in China, and infections caused by a few uncommon serovars have been reported in recent years, though not with S. Welikade. This study reports the first clinical case caused by S. Welikade in China and places Chinese S. Welikade isolates in the context of global isolates via genomic analysis. For comparison, S. Welikade isolates were also screened in the Chinese Local Surveillance System for Salmonella (CLSSS). The minimum inhibitory concentrations (MICs) of 28 antimicrobial agents were determined using the broth microdilution method. The isolates were sequenced on an Illumina platform to identify antimicrobial resistance genes, virulence genes, and phylogenetic relationships. Results: The S. Welikade isolate (Sal097) was isolated from a two-year-old boy with acute gastroenteritis in 2021. Along with the other two isolates found in CLSSS, the three Chinese isolates were susceptible to all the examined antimicrobial agents, and their sequence types (STs) were ST5123 (n = 2) and ST3774 (n = 1). Single nucleotide polymorphism (SNP)-based phylogenetic analysis revealed that global S. Welikade strains can be divided into four groups, and these three Chinese isolates were assigned to B (n = 2; Sal097 and XXB1016) and C (n = 1; XXB700). In Group B, the two Chinese ST5123 isolates were closely clustered with three UK ST5123 isolates. In Group C, the Chinese isolate was closely related to the other 12 ST3774 isolates. The number of virulence genes in the S. Welikade isolates ranged from 59 to 152. The galF gene was only present in Group A, the pipB2 gene was only absent from Group A, the avrA gene was only absent from Group B, and the allB, sseK1, sspH2, STM0287, and tlde1 were found only within Group C and D isolates. There were 15 loci unique to the Sal097 isolate. Conclusion: This study is the first to characterize and investigate clinical S. Welikade isolates in China. Responsible for a pediatric case of gastroenteritis in 2021, the clinical isolate harbored no antimicrobial resistance and belonged to phylogenetic Group B of global S. Welikade genomes. [ABSTRACT FROM AUTHOR]

Salmonella Enteritidis was the primary foodborne pathogen responsible for acute gastroenteritis. The growing ceftriaxone resistance poses a significant threat to public health. Infection with S. Enteritidis has emerged as a major public health concern, particularly in developing countries. However, research on ceftriaxone-resistant S. Enteritidis (CRO-RSE) remains limited, particularly concerning its resistance mechanism, plasmid structure, and transmission characteristics. This study aims to address these gaps comprehensively. We collected 235 S. Enteritidis isolates from Hangzhou First People's Hospital between 2010 and 2020. Among these, 8.51% (20/235) exhibited resistance to ceftriaxone. Whole-genome analysis revealed that 20 CRO-RSE isolates harbored blaCTX-M-55 or blaCTX-M-14 on the plasmid. Moreover, the dissemination of the blaCTX-M-type gene was associated with IS26 and ISEcp1. Plasmid fusion entailing the integration of the p1 plasmid with antibiotic resistance genes and the p2 (pSEV) virulence plasmid was observed in certain CRO-RSE. Additionally, the structural analysis of the plasmids unveiled two types carrying the blaCTX-M-type gene: type A with multiple replicons and type B with IncI1 (Alpha) replicon. Type B plasmids exhibited superior adaptability and stability compared to type A plasmids within Enterobacteriaceae. Interestingly, although the type B (S808-p1) plasmid displayed the potential to spread to Acinetobacter baumannii, it failed to maintain stability in this species. [ABSTRACT FROM AUTHOR]

Listeria monocytogenes is an important foodborne pathogen with worldwide prevalence. Understanding the variability in the potential pathogenicity among strains of different subtypes is crucial for risk assessment. In this study, the growth, survival, and virulence characteristics of 16 L. monocytogenes strains isolated from imported meat in China (2018–2020) were investigated. The maximum specific growth rate (μmax) and lag phase (λ) were evaluated using the time-to-detection (TTD) method and the Baranyi model at different temperatures (25, 30, and 37 °C). Survival characteristics were determined by D-values and population reduction after exposure to heat (60, 62.5, and 65 °C) and acid (HCl, pH = 2.5, 3.5, and 4.5). The potential virulence was evaluated via adhesion and invasion to Caco-2 cells, motility, and lethality to Galleria mellonella. The potential pathogenicity was compared among strains of different lineages and subtypes. The results indicate that the lineage I strains exhibited a higher growth rate than the lineage II strains at three growth temperatures, particularly serotype 4b within lineage I. At all temperatures tested, serotypes 1/2a and 1/2b consistently demonstrated higher heat resistance than the other subtypes. No significant differences in the log reduction were observed between the lineage I and lineage II strains at pH 2.5, 3.5, and 4.5. However, the serotype 1/2c strains exhibited significantly low acid resistance at pH 2.5. In terms of virulence, the lineage I strains outperformed the lineage II strains. The invasion rate to Caco-2 cells and lethality to G. mellonella exhibited by the serotype 4b strains were higher than those observed in the other serotypes. This study provides meaningful insights into the growth, survival, and virulence of L. monocytogenes, offering valuable information for understanding the correlation between the pathogenicity and subtypes of L. monocytogenes. [ABSTRACT FROM AUTHOR]

Foodborne pathogenic bacteria have long been one of the food safety hazards in China. How to control effectively the proliferation of foodborne pathogenic bacteria in food has always been a hot topic. Based on the single factor experiments of plasma activated lactic acid (PALA) volume concentration, activation time and reaction time, taking Escherichia coli, Salmonella Enteritidis, Staphylococcus aureus and Listeria monocytogenes as the model strains, and the total number of colonies as the response value, the effects of the PALA on four foodborne pathogens were investigated in this study. The results showed that the killing rates of four foodborne pathogens increased with an increase of the PALA volume concentration, extension of activation time and prolongation of reaction time in certain ranges. When the PALA was activated for 120 seconds, the volume concentration was 0.2%, and the reaction between PALA and the four foodborne pathogens lasted for 10 minutes, about 7.71 lg CFU/mL of Escherichia coli, 4.52 lg CFU/mL of Salmonella, 4.03 lg CFU/mL of Staphylococcus aureus and 3.90 lg CFU/mL of Listeria monocytogenes in pure culture were killed. The killing rates of 4 kinds of the pure culture foodborne pathogens reached 99.9% (P<0.05), and more than 3.9 logarithm of the total number of colonies of pathogenic bacteria were killed. In summary, PALA can rapidly and efficiently kill common foodborne pathogens. [ABSTRACT FROM AUTHOR]

Listeria monocytogenes is an important pathogen that can cause listeriosis. Despite the growing recognition of Listeria spp. as a foodborne and environmental pathogen, the understanding of its prevalence and characteristics of Listeria spp. in the marine environment remains unknown. In this study, we first investigated the genetic and phenotypic characteristics of Listeria species isolated in a coastal city in China. The findings revealed that the sequence type 87 (ST87) L. monocytogenes, a prevalent clinical and seafood strain in China, dominates in recreational beach sands and possesses a notable biofilm-forming capacity in seawater. The presence of ST87 L. monocytogenes in coastal environments indicates the potential health risks for both recreational activities and seafood consumption. Moreover, the ST121 isolates from sand had a versatile plasmid encoding multifunctional genes, including uvrX for UV resistance, gbuC for salt resistance, and npx for oxidative resistance and multiple transposases, which potentially aid in survival under natural environments. Black-headed gulls potentially facilitate the spread of L. monocytogenes, with similar ST35 strains found in gulls and beach sand. As a reservoir of microbes from marine environments and human/animal excrement, coastal sand would play an important role in the spread of L. monocytogenes and is an environmental risk for human listeriosis. [ABSTRACT FROM AUTHOR]

Cronobacter spp. are emerging foodborne pathogens that cause severe diseases. However, information on Cronobacter contamination in quick-frozen foods in China is limited. Therefore, we studied the prevalence, molecular characterization, and antimicrobial susceptibility of Cronobacter in 576 quick-frozen food samples collected from 39 cities in China. Cronobacter spp. were found in 18.75% (108/576) of the samples, and the contamination degree of the total positive samples was 5.82 MPN/g. The contamination level of frozen flour product samples was high (44.34%). Among 154 isolates, 109 were C. sakazakii, and the main serotype was C. sakazakii O1 (44/154). Additionally, 11 serotypes existed among four species. Eighty-five sequence types (STs), including 22 novel ones, were assigned, indicating a relatively high genetic diversity of the Cronobacter in this food type. Pathogenic ST148, ST7, and ST1 were the main STs in this study. ST4, epidemiologically related to neonatal meningitis, was also identified. All strains were sensitive to cefepime, tobramycin, ciprofloxacin, and imipenem, in which the resistance to cephalothin was the highest (64.94%).Two isolates exhibited multidrug resistance to five and seven antimicrobial agents, respectively. In conclusion, these findings suggest that the comparatively high contamination level of Cronobacter spp. in quick-frozen foods is a potential risk warranting public attention. [ABSTRACT FROM AUTHOR]

Allium tenuissimum L. as a kind of food condiment in northern China, is popular among more and more consumers owning to its special flavor from the flower. However, its composition has not been widely studied. Hence, the aim of this study was to investigate the chemical composition and antimicrobial and antioxidant activity of essential oil from Allium tenuissimum L. flowers. Gas chromatography–mass spectrometry (GC-MS) was applied to detect the chemical composition. The antimicrobial activity against foodborne pathogens was evaluated by measuring the zones of inhibition (ZOI), the minimal inhibitory concentration (MIC), and the minimal bactericidal concentration (MBC). The antioxidant effect was tested by the scavenging capacity on DPPH, ABTS+•, and •OH. The results of GC-MS showed that 72 volatile components were isolated and the structures 68 of them were identified, which comprised about 91.92% of the total composition of the oil. Among these compounds, terpenoid compounds and sulfurous compounds had the highest contents, especially dimethyl trisulfide. Our investigation demonstrated that the essential oil has better antimicrobial efficiency to Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Aspergillus flavus, and Saccharomyces cerevisiae. In addition, the essential oil had a strong stability to UV. Furthermore, the essential oil exhibited a high radical-scavenging effect on DPPH, ABTS+•, and •OH, which is significant for application in the food industry. In conclusion, the essential oil could be used as an inexpensive and natural antibacterial and antioxidant agent in food. [ABSTRACT FROM AUTHOR]

Salmonella are widely distributed foodborne pathogens and are often associated with food animal products. Colistin resistance mediated by mcr-1 is an increasing threat; however, data on the characteristics of mcr-1-harboring Salmonella among retail foods are still lacking. In this study, retail meats from 24 supermarkets and eggs from nine markets in Qingdao city were investigated to determine the presence and genomic characteristics of mcr-1-harboring Salmonella. We found the retail meats and eggs were highly contaminated by Salmonella, with detection rates of 17.5% (31/177) and 12.3% (16/130), respectively. A total of 76 Salmonella isolates were obtained in this study, and 77.6% showed multidrug resistance (MDR). The MDR proportion of egg isolates (97.5%) was significantly higher than that in meat isolates (55.6%) (p < 0.05). The most prevalent Salmonella serotypes were Typhimurium (56.6%) and Enteritidis (17.1%). Of the 76 Salmonella isolates, 40 possessed mcr-1. All 40 mcr-1-positive isolates were ST34 S. Typhimurium and were from eggs of eight brands. Different mcr-1-harboring isolates existed in the same egg, and some isolates from different egg samples or brands showed clonal relationships. The mcr-1 was located on similar IncHI2/HI2A MDR non-conjugative plasmids lacking transfer region, resulting in the failure of conjugation. The phylogenetic tree using genome sequences showed that the mcr-1-positive isolates from eggs clustered together with mcr-1-positive isolates from chicken and humans in China, revealing that mcr-1-positive egg-borne Salmonella might be derived from chicken and could potentially trigger outbreaks in humans. The high occurrence of mcr-1-harboring Salmonella in fresh eggs is alarming, and there is an urgent need to monitor mcr-1-harboring Salmonella in retail meats and eggs. We report for the first time the role of retail eggs in disseminating mcr-1-positive Salmonella and the risk of transmission of these MDR pathogens from retail food to humans should be evaluated comprehensively. [ABSTRACT FROM AUTHOR]

Highlights: Systematic analyzation to assess the spread of AMR bacteria prevalence in retail food products and the subsequent exposure to antibiotic resistance. Out of 13,018 food samples, 5000 samples were contaminated. Meat shows high to medium potential of AMR exposure for Gram-positive and Gram-negative foodborne pathogens. Salmonella and Staphylococcus aureus were two predominant bacteria seen in China and the USA, respectively. Multidrug resistance was detected in most of the food samples from both countries. Food samples were more resistant to β-lactams and tetracyclines. Government bodies were formed to tackle AMR from food. Since the discovery of antibiotics in the 20th century, they have been used to fight against infections. The overuse of antibiotics in the wider environment has resulted in the emergence of multidrug-resistant bacteria. In developing countries such as China and developed countries such as the USA, there is evidence of the high pervasiveness of antibiotic-resistant infections. However, the studies on the spread of antibiotic-resistant microorganisms that inform about the consequences are limited. The aim of our study was to analyze and compare antimicrobial resistance (AMR) identified in published research papers from that found in different food sources, which were published between 2012 and December 2021, covering most retail food items. Out of 132 research papers identified, 26 papers have met our strict criteria and are included in the qualitative and quantitative analysis. The selected papers led to 13,018 food samples, out of which 5000 samples were contaminated, including 2276 and 2724 samples from China and the USA, respectively. Meat, aquatic products, milk, and eggs show high to medium potential for AMR exposure to Gram-positive bacteria such as Staphylococcus, Enterococci, etc. and Gram-negative foodborne pathogens such as Campylobacter, Salmonella, Vibrio, etc. Most of the food samples show antibiotic resistance to β-lactams, tetracycline, quinolones, and aminoglycosides. Retail food products such as meat, sea food, and some other food products, as well as AMR genetics and technically important bacteria, are proposed to be better merged with mitigation strategies and systematic One Health AMR surveillance to minimize the knowledge gaps and facilitate comprehensive AMR risk computation for the consumers. [ABSTRACT FROM AUTHOR]

Antibiotic growth promoters (AGPs) have been used as feed additives to improve feed efficiency in food animals for more than six decades. However, the wide use of AGPs has led to the emergence of antibiotic-resistant pathogens of animal origin, posing a significant threat to food safety and public health. China prohibited the addition of AGPs to animal feed from July 2020. The impacts caused by the withdrawal of AGPs on the prevalence and antibiotic resistance of foodborne pathogens have not been illustrated. Here, a total of 471 strains of Campylobacter were isolated from pigs from three pig farms and two slaughterhouses in Sichuan Province for 4 consecutive years (2018-2021), including 2 years before and 2 years after the ban on AGPs in China. The isolation rate of Campylobacter had a slight increase after prohibiting the addition of AGPs to the feed. Contrary to what we expected, the antibiotic susceptibility test and WGS data showed that the antibiotic resistance to gentamicin and florfenicol and the abundance of virulence genes increased significantly after the ban of AGPs. Comparison of the isolates of swine origin with isolates of human origin indicated the potential of antibiotic-resistant Campylobacter transmission from pigs to humans. These data suggested that phasing out AGPs may lead to increased use of therapeutic antimicrobials, promoting the prevalence and transmission of both antibiotic resistance and virulence genes. [ABSTRACT FROM AUTHOR]

Cronobacter spp. is an important foodborne pathogen that can cause life‐threatening diseases in infants and immunocompromised adults. The present study was carried out to understand the prevalence and characterization of Cronobacter spp. in dried edible mushrooms in Jiangsu province, China. Cronobacter isolates were identified and genotyped by multilocus sequence typing (MLST); the antimicrobial susceptibility of Cronobacter strains was determined by the disk diffusion method; the biofilm formation ability of Cronobacter spp. was assessed using the microtiter plate method. The overall prevalence of Cronobacter spp. in dried edible mushrooms was 14.8%, with the highest contamination rate of after 37.2% found in Auricularia auricular. The Cronobacter isolates were identified as C. sakazakii (n = 26), C. malonaticus (n = 2), C. dublinensis (n = 2) and C. turicensis (n = 1). The MLST scheme produced 20 sequence types (STs), two of which were newly identified. ST148 was the most prevalent ST (n = 5), followed by ST4 (n = 3), ST17 (n = 3), ST64 (n = 3), and ST540 (n = 2). One (3.2%) and 15 (48.4%) Cronobacter isolates were resistant to tetracycline and meropenem, respectively. In contrast, all of the tested isolates were susceptible to the remaining 14 antibiotics. Moreover, 20 (64.5%) Cronobacter isolates showed weak ability to produce biofilm, but no isolates showed strong or moderate biofilm‐forming ability. Practical Application: Our findings revealed a high genetic diversity of Cronobacter spp. in dried edible mushrooms and provided new epidemiological evidence for the widespread existence of Cronobacter spp. in such products. The presence of Cronobacter spp. in dried edible mushrooms may pose potential risks to human health and enhancing the hygiene of such products are necessary to ensure food safety. [ABSTRACT FROM AUTHOR]

Background: Salmonella is a leading foodborne and zoonotic pathogen, and is widely distributed in different nodes of the pork supply chain. In recent years, the increasing prevalence of antimicrobial resistant Salmonella poses a threat to global public health. The purpose of this study is to the prevalence of antimicrobial resistant Salmonella in pig slaughterhouses in Hubei Province in China, and explore the effect of using lytic bacteriophages fighting against antimicrobial resistant Salmonella. Results: We collected a total of 1289 samples including anal swabs of pigs (862/1289), environmental swabs (204/1289), carcass surface swabs (36/1289) and environmental agar plates (187/1289) from eleven slaughterhouses in seven cities in Hubei Province and recovered 106 Salmonella isolates. Antimicrobial susceptibility testing revealed that these isolates showed a high rate of antimicrobial resistance; over 99.06% (105/106) of them were multidrug resistant. To combat these drug resistant Salmonella, we isolated 37 lytic phages using 106 isolates as indicator bacteria. One of them, designated ph 2–2, which belonged to the Myoviridae family, displayed good capacity to kill Salmonella under different adverse conditions (exposure to different temperatures, pHs, UV, and/or 75% ethanol) and had a wide lytic spectrum. Evaluation in mouse models showed that ph 2–2 was safe and saved 80% (administrated by gavage) and 100% (administrated through intraperitoneal injection) mice from infections caused by Salmonella Typhimurium. Conclusions: The data presented herein demonstrated that Salmonella contamination remains a problem in some pig slaughter houses in China and Salmonella isolates recovered in slaughter houses displayed a high rate of antimicrobial resistance. In addition, broad-spectrum lytic bacteriophages may represent a good candidate for the development of anti-antimicrobial resistant Salmonella agents. [ABSTRACT FROM AUTHOR]

Simple Summary: Non-typhoid Salmonella is the general term of Salmonella other than typhoid and paratyphoid, which often causes foodborne gastroenteritis in humans, but some serotypes have been proved to be pathogenic to poultry. Salmonella Enterica and Salmonella Typhimurium are the common serotypes pathogenic to poultry and have been systematically studied, but other serotypes have rarely been studied. During Salmonella surveillance in farms, we discovered by chance that Salmonella Thompson, a common non-typhoid Salmonella, is also pathogenic to avian embryos. Therefore, this study aimed to explore antimicrobial resistance and pathogenicity of clinical S. Thompson. Firstly, we found that the core-genome multilocus sequence typing of 14 clinical S. Thompson was consistent with two strains of S. Thompson from humans in China. Secondly, the antimicrobial resistance gene analysis demonstrated that all strains carried the polymyxin resistance gene mcr-9, which had not appeared resistance phenotype. Meanwhile, many essential virulence genes were also found in each S. Thompson isolate. Finally, the bacterial inoculation experiment revealed that clinical S. Thompson was highly pathogenic to newborn chicks after yolk sac inoculation. This study suggests that Salmonella Thompson can circulate between humans and poultry farms and transmit drug resistance genes and demonstrated that Salmonella Thompson is highly pathogenic to chicks and should be guarded against in the hatching stage of poultry farms. Salmonella Thompson, an important foodborne pathogen, is rarely found to be pathogenic to poultry. Accidentally, S. Thompson was found to be pathogenic to embryos of white feather broiler at a poultry farm in China. Therefore, this study aimed to explore antimicrobial resistance and pathogenicity of clinical S. Thompson isolated from dead poultry embryos. The phylogenetic tree based on 16S rRNA and seven housekeeping genes showed that the 14 clinical S. Thompson were closely related. The core-genome multilocus sequence typing of 14 clinical S. Thompson based on whole-genome sequencing was cgST-12774, consistent with the only two strains of S. Thompson from humans in China as reported in the NCBI database. The antimicrobial resistance gene analysis demonstrated that all strains carried aac(6′)-Iaa and the polymyxin resistance gene mcr-9. Antimicrobial sensitivity tests for 18 antibiotics showed that S. Thompson isolates displayed resistance against streptomycin (100%), ampicillin (35.7%), and doxycycline (14.3%), but sensitivity to polymyxin B, proving that the mcr-9 gene had not appeared resistance phenotype. Virulence genes Salmonella pathogenicity island (SPI) SPI1-5, type I fimbriae gene (fimA), flagellar assembly genes (bcfC, flhD, fliA, fliC, fljB, flgK, and lpfC), and other virulence genes (iroN, pagC, and cigR) were found in each S. Thompson isolate. Additionally, the bacterial inoculation experiment with 1-day-old chicks revealed that clinical S. Thompson was highly pathogenic to newborn chicks after yolk sac inoculation. This study highlighted that the S. Thompson isolated from poultry embryos and the S. Thompson causing human foodborne diarrhea in some parts of China belong to the same cgMLST typology (cgST-12774) and showed the pathogenicity of this clinical S. Thompson to chicks. [ABSTRACT FROM AUTHOR]

Campylobacter jejuni is recognized as a significant foodborne pathogen, and recent studies have indicated a rising trend of aminoglycosides resistance gene aph(2″)-If among C. jejuni isolates from food-producing animals in China. However, systematic information about aph(2″)-If -positive C. jejuni from food-producing animals and other sources worldwide based on whole-genome analysis remains a knowledge gap. In this study, we aimed to analyze the worldwide distribution, genetic environment and phylogenetic tree of aph(2″)-If by utilizing Whole Genome Sequencing (WGS) data obtained, coupled with information in the GenBank database. A total of 160 C. jejuni isolates in the GenBank database and 14 C. jejuni isolates in our laboratory carrying aph(2″)-If gene were performed for further analysis. WGS analysis revealed the global distribution of aph(2″)-If among C. jejuni from 6 countries. Multilocus Sequence Typing(MLST) results indicated that 70 STs were involved in the dissemination of aph(2″)-If , with ST10086 being the predominant ST. Whole-genome Multilocus Sequence Typing(wg-MLST) analysis according to times, countries, and origins of C. jejuni isolation further demonstrated a close relationship between aph(2″)-If carrying C. jejuni isolates from farm and food. The findings also revealed the existence of 32 distinct types of genetic environments surrounding aph(2″)-If among these isolates. Notably, Type 30, characterized by the arrangement IS sag10 - deoD - ant (9)- hp - hp - aph(2″)-If , emerged as the predominant genetic environment. In conclusion, our analysis provides the inaugural perspective on the worldwide distribution of aph(2″)-If. This resistance gene demonstrates horizontal transferability and regional diffusion in a clonal pattern. The close association observed among aph(2″)-If -positive C. jejuni strains isolated from poultry, food, and clinical environments underscores the potential for zoonotic transmission from these isolates. • aph(2″)-If is globally prevalent among C. jejuni, indicating its widespread. • Close correlation was identified between aph(2″)-If- positive C. jejuni of different origin. • Diverse genetic environments highlights aph(2″)-If widely dissemination. [ABSTRACT FROM AUTHOR]

Salmonella Thompson is a prevalent foodborne pathogen and a major threat to food safety and public health. This study aims to reveal the dissemination mechanism of S. Thompson with co-resistance to ceftriaxone and ciprofloxacin. In this study, 181 S. Thompson isolates were obtained from a retrospective screening on 2118 serotyped Salmonella isolates from foods and patients, which were disseminated in 12 of 16 districts in Shanghai, China. A total of 10 (5.5 %) S. Thompson isolates exhibited resistance to ceftriaxone (MIC ranging from 8 to 32 μg/mL) and ciprofloxacin (MIC ranging from 2 to 8 μg/mL). The AmpC β-lactamase gene bla CMY-2 and plasmid-mediated quinolone resistance (PMQR) genes of qnr S and qep A were identified in the 9 isolates. Conjugation results showed that the co-transfer of bla CMY-2 , qnr S, and qep A occurred on the IncC plasmids with sizes of ∼150 (n = 8) or ∼138 (n = 1) kbp. Three typical modules of IS Ecp1 - bla CMY-2 - blc-sugE , IS 26 -IS 15DIV-qnr S-IS Kpn19 , and IS CR3 - qep A-intl1 were identified in an ST3 IncC plasmid pSH11G0791. Phylogenetic analysis indicated that IncC plasmids evolved into Lineages 1, 2, and 3. IncC plasmids from China including pSH11G0791 in this study fell into Lineage 1 with those from the USA, suggesting their close genotype relationship. In conclusion, to our knowledge, it is the first report of the co-existence of bla CMY-2 , qnr S, and qep A in IncC plasmids, and the conjugational transfer contributed to their dissemination in S. Thompson. These findings underline further challenges for the prevention and treatment of Enterobacteriaceae infections posed by IncC plasmids bearing bla CMY-2 , qnr S, and qep A. • Ceftriaxone and ciprofloxacin co-resistance was found in Salmonella Thompson. • Co-transfer of blaCMY-2, qnrS and qepA occurred on the IncC plasmids. • ISEcp1-blaCMY-2-blc-sugE, IS26-IS15DIV-qnrS-ISKpn19 and ISCR3-qepA-intl1 were found. • IncC plasmids from China fell into Lineage 1 with those from the USA. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Preventive Veterinary Medicine / Zhongguo Yufang Shouyi Xuebao is the property of Chinese Journal of Preventive Veterinary Medicine Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Salmonella enterica (S. enterica) is an important foodborne pathogen, causing food poisoning and human infection, and critically threatening food safety and public health. Salmonella typing is essential for bacterial identification, tracing, epidemiological investigation, and monitoring. Serotyping and multilocus sequence typing (MLST) analysis are standard bacterial typing methods despite the low resolution. Core genome MLST (cgMLST) is a high-resolution molecular typing method based on whole genomic sequencing for accurate bacterial tracing. We investigated 250 S. enterica isolates from poultry, livestock, food, and human sources in nine provinces of China from 2004 to 2019 using serotyping, MLST, and cgMLST analysis. All S. enterica isolates were divided into 36 serovars using slide agglutination. The major serovars in order were Enteritidis (31 isolates), Typhimurium (29 isolates), Mbandaka (23 isolates), and Indiana (22 isolates). All strains were assigned into 43 sequence types (STs) by MLST. Among them, ST11 (31 isolates) was the primary ST. Besides this, a novel ST, ST8016, was identified, and it was different from ST40 by position 317 C → T in dnaN. Furthermore, these 250 isolates were grouped into 185 cgMLST sequence types (cgSTs) by cgMLST. The major cgST was cgST235530 (11 isolates), and only three cgSTs contained isolates from human and other sources, indicating a possibility of cross-species infection. Phylogenetic analysis indicated that most of the same serovar strains were putatively homologous except Saintpaul and Derby due to their multilineage characteristics. In addition, serovar I 4,[5],12:i:- and Typhimurium isolates have similar genomic relatedness on the phylogenetic tree. In conclusion, we sorted out the phenotyping and genotyping diversity of S. enterica isolates in China during 2004–2019 and clarified the temporal and spatial distribution characteristics of Salmonella from different hosts in China in the recent 16 years. These results greatly supplement Salmonella strain resources, genetic information, and traceability typing data; facilitate the typing, traceability, identification, and genetic evolution analysis of Salmonella ; and therefore, improve the level of analysis, monitoring, and controlling of foodborne microorganisms in China. [ABSTRACT FROM AUTHOR]

Copyright of Shipin Kexue/ Food Science is the property of Food Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Background: Intensive aquaculture farming has caused significant degradation of coastal wetlands and has been proposed as a reservoir for pathogenic Vibrio spp. Results: Gut pathogens including Vibrio spp., Salmonella spp., and Klebsiella spp. were isolated from bird feces, shrimp and wetland water in two typical coastal regions of China in 2015 and 2017 and were subsequently subjected to whole-genome sequencing. Meanwhile, local patient isolates were also selected to confirm the epidemiological links. Bacterial community composition analyses of the sediments that were sampled in 2015 and 2017 were conducted by the hypervariable region 4 of the 16S rRNA gene. Together with the local clinical isolates, we observed highly related Vibrio isolates from waterbirds, wetlands and shrimp. Phylogenetic genome comparisons also demonstrated that sequence types ST3 and ST2414 Vibrio parahaemolyticus isolates obtained from aquatic animals were clonally related to patient isolates. Likewise, three Salmonella typhimurium isolates were also genomically related to one clinical strain. The results showed that farming activities significantly altered the community composition and resulted in the emergence of several pathogens, including Acinetobacter, Mycobacterium and Legionella. Conclusions: In conclusion, our results demonstrated that intensive shrimp farming in wetlands has two devastating impacts: pathogen dissemination from aquatic animals into migratory birds and transmission of foodborne pathogens into local communities. [ABSTRACT FROM AUTHOR]

Vibrio parahaemolyticus, a leading foodborne pathogen that occurs naturally in estuarine and marine environments worldwide, is responsible for raising food safety issues in China. The global dissemination of this pathogen underscores the importance of understanding its virulence factors and their effects on the human host. We herein obtained and compared the secretomic profiles of the virulent ATCC17802 strain and the avirulent JHY32 strain of V. parahaemolyticus. In total, 28 extracellular proteins were identified, and most proteins that were differentially expressed in ATCC17802 were related to toxicity and environmental adaptability. In addition, various extracellular proteins with unknown function and potential virulence factors were identified. Our results provide data that can be used for the development of novel vaccines against V. parahaemolyticus. [ABSTRACT FROM AUTHOR]

Salmonella is an important food pathogen that can cause severe gastroenteritis with more than 600,000 deaths globally every year. Colistin (COL), a last-resort antibiotic, is ineffective in bacteria that carry a functional mcr-1 gene, which is often spread by conjugative plasmids. Our work aimed to understand the prevalence of the mcr-1 gene in clinical isolates of Salmonella , as the frequency of occurrence of the mcr-1 gene is increasing globally. Therefore, we analyzed 689 clinical strains, that were isolated between 2009 and late 2018. The mcr-1 gene was found in six strains, which we analyzed in detail by whole genome sequencing and antibiotic susceptibility testing, while we also provide the clinical information on the patients suffering from an infection. The genomic analysis revealed that five strains had plasmid-encoded mcr-1 gene located in four IncHI2 plasmids and one IncI2 plasmid, while one strain had the chromosomal mcr-1 gene originated from plasmid. Surprisingly, in two strains the mcr-1 genes were inactive due to disruption by insertion sequences (ISs): IS Apl1 and IS Vsa5. A detailed analysis of the plasmids revealed a multitude of ISs, most commonly IS 26. The IS contained genes that meditate broad resistance toward most antibiotics underlining their importance of the mobile elements, also with respect to the spread of the mcr-1 gene. Our study revealed potential reservoirs for the transmission of COL resistance and offers insights into the evolution of the mcr-1 gene in Salmonella. [ABSTRACT FROM AUTHOR]

Listeria monocytogenes is an etiologic agent of listeriosis, and has emerged as an important foodborne pathogen worldwide. In this study, the molecular characteristics of 155 L. monocytogenes isolates from seven food groups in Shanghai, the biggest city in China, were identified using whole-genome sequencing (WGS). Most L. monocytogenes isolates (79.3%) were obtained between May and October from 2009 to 2019. The serogroups and clonal complexes (CCs) of L. monocytogenes were found useful for identifying potential health risks linked to foods. Differences in distributions of serogroups and CCs among different food groups were analyzed using t -test. The results showed that the IIa and IVb serogroups were identified among most of food groups. However, the prevalence of serogroup IIb was significantly higher in ready-to-eat (RTE) food and raw seafood than in other food groups, similar to group IIc in raw meat and raw poultry than others. Meanwhile, the prevalence of CC9 in raw meat and raw poultry, CC8 in raw poultry, and CC87 in raw seafood significantly exceeded that of in other food groups. Specially, CC87 was the predominant CC in foodborne and clinical isolates in China, indicating that raw seafood may induce a high-risk to food safety. Also, hypervirulence pathogenicity islands LIPI-3 and LIPI-4 were found in CC3, CC1, and CC87, respectively. The clonal group CC619 carried LIPI-3 and LIPI-4, as previously reported in China. Core genome multilocus sequence typing (cgMLST) analysis suggested that CC87 isolates from the same food groups in different years had no allelic differences, indicating that L. monocytogenes could persist over years. These 10-year results in Shanghai underscore the significance of molecular epidemiological surveillance of L. monocytogenes in foodborne products in assessing the potential risk of this pathogen, and further address food safety issues in China. [ABSTRACT FROM AUTHOR]

Information on the burden of disease due to foodborne pathogens in China is quite limited. To understand the incidence of foodborne gastroenteritis due to non-typhoidal Salmonella enterica and Vibrio parahaemolyticus, population survey and sentinel hospital surveillance were conducted during July 2010 to June 2011 in Shanghai, east China, and a model for calculating disease burden was established. The multiplier for gastroenteritis caused by these pathogens was estimated at 59 [95% confidence interval (CI) 30–102]. Annual incidence per 100,000 population in Shanghai was estimated as 48 (95% CI 24–83) and 183 (95% CI 93–317) cases for foodborne non-typhoidal salmonellosis and V. parahaemolyticus gastroenteritis, respectively, illustrating that bacterial gastroenteritis due to these two pathogens poses a substantial health burden. There is a significant difference between our simulated incidence and the data actually reported for foodborne diseases, indicating significant underreporting and underdiagnosis of non-typhoidal S. enterica and V. parahaemolyticus gastroenteritis in the surveillance area. The present research demonstrates basic situation of the health burden caused by major foodborne pathogens in the surveillance area. Enhanced laboratory-based sentinel hospital surveillance is one of the effective ways to monitor food safety in east China. [ABSTRACT FROM AUTHOR]

Background: Polymyxins are currently regarded as a possible last-resort therapy to eradicate multidrug-resistant (MDR) gram-negative bacteria. Meanwhile, the old antimicrobial agent fosfomycin has recently been reintroduced into clinical use for the treatment of extended-spectrum β-lactamase (ESBL)-producing and carbapenem-resistant Enterobacteriaceae. This study investigated a multidrug-resistant Salmonella 4,[5],12:i:- strain from a food catering handler, which had the potential to act as a vehicle for transmitting MDR foodborne pathogens. Methods: A Salmonella 4,[5],12:i:- YZU1189 strain was isolated from the fecal sample of a food catering worker according to the standard protocol of the Salmonella detection method from World Health Organization in 2003. Serotyping of YZU1189 was performed according to the Kauffmann–White scheme. The antimicrobial resistance phenotype of the strain was determined by the agar dilution method according to the instruction from Clinical and Laboratory Standards Institute (CLSI). Plasmid conjugation was performed between the donor strain Salmonella 4,[5],12:i:- YZU1189 and the recipient strain Escherichia coli C600. The genetic locations of mcr-1, blaCTX-M-14 and fosA3 genes were determined by the whole genome sequence analysis. Results: Salmonella 4,[5],12:i:- YZU1189 was an ESBL-producing stain isolated from a healthy catering worker. The strain displayed resistance to aminoglycosides, beta-lactams, polymyxins, fosfomycins, phenicols, trimethoprims, sulfonamides, tetracyclines and fluoroquinolones. Whole genome sequence analysis and plasmid conjugation revealed that the strain had a transferable IncHI2 plasmid carrying the mcr-1, blaCTX-M-14 and fosA3 genes. Sequence homology analysis showed that this plasmid possessed high sequence similarity to previously reported mcr-1, blaCTX-M-14 and fosA3 positive plasmids in China. Conclusion: This study reported a the multidrug-resistant Salmonella 4,[5],12:i:- isolate harboring mcr-1, blaCTX-M-14 and fosA3 from human for the first time in China. The occurrence of mcr-1 and fosA3 genes in the transferable IncHI2 plasmid pYZU1189 from the ESBL-producing Salmonella 4,[5],12:i:- isolate showed a potential threat to public health. Great concern should be taken for the spread of multidrug-resistant ESBL-producing Salmonella isolates from food catering workers to consumers. [ABSTRACT FROM AUTHOR]

Non-O157 Shiga toxin--producing Escherichia coli (STEC) strains are significant foodborne pathogens that can cause acute diarrhea in humans. This study was conducted to investigate the contamination by non-O157 STEC in different types of food sold at retail markets in the People's Republic of China and to characterize non-O157 STEC strains. From May 2012 to April 2014, 1,200 retail food samples were collected from markets in 24 cities in China. Forty-four non-O157 isolates were recovered from 43 STEC-positive samples. Of the isolates, 22 and 19 carried the stx1 and stx2 genes, respectively, and 3 harbored both stx1 and stx2. stx1a and stx2a were the most prevalent stx subtypes. Other virulence genes, ent, hlyA, astA, eae, espB, iha, subAB, and tia, were commonly detected. Diverse O serogroups were identified among these isolates. Multilocus sequence typing indicated the high genetic diversity of the isolates. Thirty-two sequence types (STs) were identified among the 44 isolates, with ST383 (9.09%), ST134 (6.82%), and ST91 (6.82%) the most prevalent. Nine new STs were found. The isolates had a high prevalence of resistance to cephalothin, ampicillin, tetracycline, trimethoprim-sulfamethoxazole, nalidixic acid, streptomycin, and chloramphenicol. Twenty isolates (45.45%) were resistant to at least three antibiotics. This study provides updated surveillance data for non-O157 STEC isolates from foods sold at retail markets. Virulent and multidrug-resistant non-O57 STEC strains were isolated from all types of food. Our findings highlight the need for increased monitoring of non-O157 STEC in retail foods. [ABSTRACT FROM AUTHOR]

Pickled ready-to-eat meat (PRTEM) is a meat product that is treated with various seasonings and then cooked. PRTEM is a popular food consumed mostly in China and some Asian countries. Since this food is considered 'ready to eat', once it is contaminated by foodborne pathogens such as Salmonella , the prospect for significant morbidity, mortality, and immeasurable economic losses can occur. Here we investigated the prevalence and concentration of Salmonella in 107 PRTEM samples collected from Shaanxi, China during 2015–2016. Furthermore, we analyzed the serotype, antibiotic susceptibility, and presence of antibiotic resistance genes and amino acid mutations in 219 Salmonella isolates, followed by subtyping of 115 representative isolates. The average detection rate of Salmonella -positive PRTEM was 58.9%, and the average most probable number (MPN) of Salmonella in positive samples was 2.27 logMPN per gram of sample (range: 2.10–2.43). Ten serotypes were identified from the 219 Salmonella isolates, with S. Thompson (37.9%) and S. Indiana (20.5%) being predominant. The remaining serotypes were S. Typhi (7.8%), S. Typhimurium (7.3%), S. Mbandaka (6.9%), S. Albany (6.4%), S. Blockley (5.5%), S. Infantis (4.1%), S. Escanaba (3.2%), and S. Dusseldorf (0.5%). All isolates were resistant to ceftiofur (100%), while most of them were resistant to ciprofloxacin (99.1%), amoxicillin-clavulanic acid (97.7%), trimethoprim-sulfamethoxazole (96.4%), ampicillin (92.3%), sulfisoxazole (92.2%), tetracyclines (90.4%), and nalidixic acid (90.4%), respectively. A single mutation of Ser83Phe (27.1%) and double mutations of Ser83Phe-Asp87Gly (25.9%) in GyrA were detected in 85 isolates, whereas mutations of Thr57Ser (63.9%) and Ser80Arg (36.1%) in ParC were detected in 122 isolates. qnr B, oqx AB, aac(6′)-Ib , and qnr A were present in 50 (22.8%), 48 (21.9%), 26 (11.9%), and 1 (0.5%) isolate(s), respectively. Pulse field gel electrophoresis results revealed that those isolates recovered from the same type of PRTEM or the same sampling place shared identical or similar DNA profiles, antibiotic resistance phenotypes, and even plasmid-mediated quinolone resistance encoding genes. The findings indicate that Salmonella is commonly prevalent in PRTEMs at high concentrations in Shaanxi, China. More attention should be paid to the processing and storage of this ready-to-eat food to prevent bacterial contamination and foodborne outbreaks. [ABSTRACT FROM AUTHOR]

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Listeria monocytogenes is an important foodborne pathogen causing public concern. A total of 3354 retail foods in bulk were sampled and screened for L. monocytogenes. Seventy-three (2.2%) samples including 21 ready-to-eat (RTE) foods and 52 raw foods were confirmed positive for L. monocytogenes. Sushi and salmon sashimi occupied the top two slots in RTE foods with relatively high presence rate of 12.9 and 6.9%, respectively. Meanwhile, L. monocytogenes was found to be distributed unequally in raw foods; the presence rates in raw meat (3.5%) and poultry (3.8%) were significantly higher than that in raw seafood (1.3%). Notably, L. monocytogenes was not detected in raw freshwater food. The L. monocytogenes isolates belonged to four serotypes, 1/2a, 1/2b, 1/2c, and 4b, with the most prevalent serotype being 1/2a (47.9%). Eighteen sequence types (STs) and eighteen virulence types (VTs) containing four newly assigned VTs (VT180, VT181, VT182, and VT183) were determined via multilocus sequence typing (MLST) and multi-virulence-locus sequence typing (MVLST). Among the 73 L. monocytogenes isolates, 23 (31.5%) belonged to epidemic clones (ECs) including ECI, ECIV, ECV, ECVI, ECVIII and ECXI among which ECV was predominant. Antibiotic susceptibility tests revealed a high resistance rate (11.0%) to tetracycline. Moreover, we identified the distribution patterns of virulence genes of four Listeria pathogenicity islands (LIPI) in L. monocytogenes isolates. prfA , hly , plcA , plcB , mpl , actA genes in LIPI-1 and inlA , inlB , inlC , inlJ genes in LIPI-2 were detected in approximately all L. monocytogenes isolates. The distribution of both LIPI-3 genes and LIPI-4 genes exhibited association with lineage and ST. LIPI-4 genes were present exclusively in ST87 isolates. Relatedness analysis revealed the absence of distinct association between STs, ECs, LIPI-3 and LIPI-4 distribution and specific food groups. This study provided fundamental data for Chinese food safety authorities to grasp the contamination status of L. monocytogenes in foods, assess the potential risk of this pathogen and further address the safety issue of retail foods in bulk in China. [ABSTRACT FROM AUTHOR]

The volume of pork meat production is continuously growing in the EU over previous years due to lower food prices, higher number of reproduction sows and increased volume of pork exports to China. Consumer choices toward pork meat depend on culture, place of residence and social opportunities, as well as their perception regarding safety and quality of pork meat/meat products. The main biological hazards associated with pork meat/meat products important from the public health perspective are zoonotic food borne pathogens, bacteria and/or parasites, e.g. Salmonella spp., Yersinia enterocolitica, Listeria monocytogenes, Trichinella spp., Toxoplasma gondii and Verotoxin-producing Escherichia coli (VTEC), by decreasing order, including associated antimicrobial resistance (AMR). Pathways of infection and contamination of pork meat differ, taking into consideration the multiple entry routes for zoonotic biological hazards along the pork meat chain, from farm to the final product. Therefore, the defined level of safety of pork meat/meat products should be achieved by synergistic action of control measures effectively applied at different points along the pork meat chain and supported by the integrated risk-based food (meat) safety management system in major modules of the meat chain: pre-harvest (farm), harvest (slaughterhouse), post-harvest (meat processing, distribution, retail, consumers), as well as identification and traceability. The integrated meat safety management system should be based on good hygienic practices (GHP) and Hazard Analysis and Critical Control Points (HACCP) encompassing the science based hazard analysis and risk characterization, as well as identifying the most effective control options and risk mitigation strategies in the pork meat chain continuum. [ABSTRACT FROM AUTHOR]

Listeria monocytogenes is an important foodborne pathogen with a significant impact on public health worldwide. A great number of outbreaks caused by L. monocytogenes has been reported, especially in the United States, and European countries. However, listeriosis has not yet been included in notifiable disease in China, and thus information on this infection has been scarce among the Chinese population. In this study, we described a 3-year surveillance of listeriosis in Beijing, China. Fifty-six L. monocytogenes strains isolated from 49 clinical infectious cases (27 pregnancy-associated infections and 22 non-pregnancy-associated infections) were analyzed by serotyping, pulsed field gel electrophoresis (PFGE), multilocus sequence typing (MLST), and antimicrobial susceptibility testing between 2014 and 2016 in Beijing. The predominant serogroups were 1/2a,3a and 1/2b,3b,7 which accounted for 92% of the overall isolates. Four strains were serogroup 4b,4d,4e, isolated from patients with pregnancy-associated infections. Based on PFGE, these isolates were divided into 32 pulsotypes (PTs) and 3 clusters associated with serogroups. Ten PTs were represented by more than one isolate with PT09 containing the most number of isolates. MLST differentiated the isolates into 18 STs, without new ST designated. The three most common STs were ST8 (18.4%), ST5 (16.3%), and ST87 (12.2%), accounting for 46.9% of the isolates. STs prevalent in other parts of the world were also present in China such as ST1, ST2, ST5, ST8, and ST9 which caused maternal fetal infections or outbreaks. However, the STs and serogroup distribution of clinical L. monocytogenes in Beijing, China was different from those in other countries. Strains of ST1 and ST2 were isolated from patients with pregnancy-associated infection, whereas none of ST155 isolates caused pregnancy-associated cases. Surveillance of molecular characterization will provide important information for prevention of listeriosis. This study also enhances our understanding of genetic diversity of clinical L. monocytogenes in China. [ABSTRACT FROM AUTHOR]

Listeria monocytogenes is a globally notorious foodborne pathogen. This study aimed to qualitatively and quantitatively detect L. monocytogenes from meat and meat products in China and to establish their virulence profiles and population diversity. From 1212 meat and meat product samples, 362 (29.9%) were positive for L. monocytogenes. Of these positive samples, 90.6% (328/362) had less than 10 MPN/g, 5.5% (20/364) samples had 10–110 MPN/g, and 3.9% (14/362) of the positive samples had over 110 MPN/g. Serogroup analysis showed that the most prevalent serogroup of L. monocytogenes was I.1 (1/2a-3a), which accounted for 45.0% (123/458) of the total, followed by serogroup I.2 (1/2c-3c) that comprised 26.9%, serogroup II.1 (4b-4d-4e) that comprised 4.8%, and serogroup II.2 (1/2b-3b-7) that comprised 23.3%. A total of 458 isolates were grouped into 35 sequence types (STs) that belonged to 25 clonal complexes (CCs) and one singleton (ST619) by multi-locus sequence typing. The most prevalent ST was ST9 (26.9%), followed by ST8 (17.9%), ST87 (15.3%), ST155 (9.4%), and ST121 (7.6%). Thirty-seven isolates harbored the llsX gene (representing LIPI-3), and they belonged to ST1/CC1, ST3/CC3, ST288/CC288, ST323/CC288, ST330/CC288, ST515/CC1, and ST619, among which ST323/CC288, ST330/CC288, and ST515/CC1 were newly reported to carry LIPI-3. Seventy-five isolates carried ptsA , and they belonged to ST87/CC87, ST88/CC88, and ST619, indicating that consumers may be exposed to potential hypervirulent L. monocytogenes. Antibiotics susceptibility tests revealed that over 90% of the isolates were susceptible to 11 antibiotics; however, 40.0% of the isolates exhibited resistance against ampicillin and 11.8% against tetracycline; further, 45.0 and 4.6% were intermediate resistant and resistant to ciprofloxacin, respectively. The rise of antibiotic resistance in L. monocytogenes suggests that stricter regulations should be formulated to restrict the use of antibiotic agents in human listeriosis treatment and livestock breeding. [ABSTRACT FROM AUTHOR]

Salmonella is an important zoonotic and foodborne pathogen that can infect humans and animals, causing severe concerns about food safety and a heavy financial burden worldwide. The pathogen can adhere to living and abiotic surfaces by forming biofilms, which increases the risk of transmission and infection. In this study, we investigated the biofilm-forming ability of 243 Salmonella strains of 36 serotypes from different sources in China using microplate crystal violet staining method. The results showed that 99.6% tested strains, with the exception of one strain of S. Thompson, were capable of forming biofilms. The strains with the biofilm-forming ability of strong, medium and weak accounted for 2.88%, 24.28% and 72.43%, respectively. The strains of S. Havana and S. Hvittingfoss had the strongest biofilm-forming ability, with the OD 570 of 0.81 ± 0.02 and 0.81 ± 0.38, respectively, while the strains of S. Agona and S. Bovismorbificans had the weakest biofilm-forming ability, with the OD 570 of 0.16 ± 0.02 and 0.15 ± 0.00, respectively. Furthermore, statistical analysis results demonstrated that isolation of source had no effect on the biofilm formation ability, while the detection rates of pefABCD and ddhC were positively correlated with the biofilm formation ability of Salmonella. In particular, the detection rate of ddhC gene was more than 60% in the biofilm forming strains. These findings have important guiding significance for the investigation of pathogenesis, as well as the prevention and control of salmonellosis. • 242 Salmonella isolates belonging to 36 serotypes from different sources in China were capable of forming biofilms. • Havana and Hvittingfoss had the strongest biofilm-forming ability, while Agona and Bovismorbificans had the weakest ability. • The detection rates of pefABCD and ddhC were positively correlated with the biofilm formation ability of the strains. [ABSTRACT FROM AUTHOR]

Atypical enteropathogenic Escherichia coli (aEPEC) is an emerging pathogen that has been implicated in outbreaks of diarrhea worldwide. The objective of this study was to investigate the occurrence of aEPEC in retail foods at markets in the People's Republic of China and to characterize the isolates for virulence genes, intimin gene (eae) subtypes, multilocus sequence types (STs), and antimicrobial susceptibility. From May 2014 to April 2015, 1,200 food samples were collected from retail markets in China, and 41 aEPEC isolates were detected in 2.75% (33 of 1,200) of the food samples. The virulence genes tir, katP, etpD, efa/lifA, ent, nleB, and nleE were commonly detected in these isolates. Nine eae subtypes were detected in the isolates, among which θ (23 isolates) and β1 (6 isolates) were the most prevalent. The 41 isolates were divided into 27 STs by multilocus sequence typing. ST752 and ST10 were the most prevalent. Antibiotic susceptibility testing revealed high resistance among isolates to streptomycin (87.80%), cephalothin (73.16%), ampicillin (51.22%), tetracycline (63.42%), trimethoprim-sulfamethoxazole (43.90%), and kanamycin (43.90%). Thirty isolates (73.17%) were resistant to at least three antibiotics, and 20 (53.66 %) were resistant to five or more antibiotics. Our results suggest that retail foods in markets are important sources of aEPEC. The presence of virulent and multidrug-resistant aEPEC in retail foods poses a potential threat to consumers. Surveillance of aEPEC contamination and prudent use of antibiotics is strongly recommended in China. [ABSTRACT FROM AUTHOR]

Bacillus cereus sensu stricto is an opportunistic foodborne pathogen. The multilocus sequence type (MLST) of 74 B. cereus isolated from 513 non-random infant formula in China was analyzed. Of 64 sequence types (STs) detected, 50 STs and 6 alleles were newly found in PubMLST database. All isolates except for one singleton (ST-1049), were classified into 7 clonal complexes (CC) by BURST (n-4), in which CC1 with core ancestral clone ST-26 was the largest group including 86% isolates, and CC2, 3, 9, 10 and 13 were first reported in China. MLST profiles of the isolates from 8 infant formula brands were compared. It was found the brands might be potentially tracked by the variety of STs, such as ST-1049 of singleton and ST-1062 of isolate from goat milk source, though they could not be easily tracked just by clonal complex types of the isolates. [ABSTRACT FROM AUTHOR]

In the study, three Bacillus cereus-specific phages, named DK1, DK2 and DK3, belonging to the family Podoviridae, were isolated from Pearl River water and sludge in Guangzhou, China. The genomes of DK1, DK2 and DK3 were 27,180 bp, 26,357 bp, and 26,865 bp in length and contained 49, 45 and 46 open reading frames, respectively. Among the three phages, DK2 shared the highest genome sequence similarity (96% identity) with DK3. Genes encoding rRNA, tRNA, virulence factors and antibiotic resistance were absent in these phage genomes. In addition, comparative genomic and phylogenetic analysis revealed that they were novel phages of B. cereus. Each genome encoded a putative endolysin that might be of value for the control of the foodborne pathogen B. cereus. [ABSTRACT FROM AUTHOR]

Fresh vegetables are closely associated with foodborne disease outbreaks; however, systematic analysis of the microbiological quality of fresh vegetables and molecular information on foodborne pathogens in fresh produce are poorly reported in China. Here, we evaluated the epidemiological prevalence of coliforms via the most probable number method and characterized Salmonella and ciprofloxacin-resistant (CIPR) Escherichia coli isolates recovered from retail fresh vegetables in Shaanxi Province, China. Antimicrobial susceptibility testing, serotype determination, multilocus sequence typing (MLST), core genome multilocus sequence typing (cgMLST), antibiotic resistance encoding gene (ARG) annotation, virulence factor prediction, and functional classification were performed. Between October 2020 and September 2021, 576 samples (i.e., tomatoes, lettuces, spinaches, and cabbages) were found to be positive for coliforms, and the prevalence of coliforms showed a seasonal trend. Coliform counts of vegetables in supermarkets in Xi'an were significantly lower (P < 0.01) than that in other cities. The detection rates of Salmonella and CIPR E. coli -positive vegetables were 1 % (6/576) and 0.7 % (4/576), respectively. All isolates exhibited resistance to ≥1 antibiotics, and 92.9 % (13/14) were multidrug-resistant. One extended spectrum β-lactamase (ESBL)-producing CIPR E. coli isolate in spinach was resistant to not only three third-generation cephalosporins but also to two polymyxins. Among nine Salmonella isolates, five different serovars (S. Enteritidis , S. Indiana , monophasic variant of S. Typhimurium , S. Agona, and S. Gallinarum), four sequence types (STs; ST11, ST13, ST17, and ST34), and seven core genome STs (cgSTs) were identified. Five CIPR E. coli strains were assigned to three serovars (O101:H4, O8:H18, and O11:H25), three STs (ST44, ST48, and ST457), and four cgSTs. Coexisting amino acid mutations of Thr57Ser/Ser80Arg in ParC and Ser83Phe/Asp87Gly in GyrA in quinolone resistance-determining regions (QRDRs) might be causes for nalidixic acid resistance. Eight definite virulence profiles in eight serovars were identified. Notably, cdtB and pltA only encoded typhoid toxins and were just detected from S. Typhoid isolates were also detected from S. Indiana and monophasic S. Typhimurium , which are closely associated with swine food chain were first detected in fresh vegetables. In conclusion, our findings suggest that coliform contamination on fresh vegetables is prevalent in this province. Most Salmonella and CIPR E. coli isolates were phenotypically and genetically diverse and could resist multiple antibiotics by carrying multiple ARGs and virulence genes. [Display omitted] • All fresh vegetables were positive for coliforms with high level. • 5 serovars, 4 STs and 7 cgSTs were identified from 9 Salmonella isolates. • 3 serovars, 3 STs and 4 cgSTs were identified from 5 CIPR E. coli isolates. • Monophasic S. Typhimurium is firstly identified from fresh vegetables. • Typhoid-associated virulence genes, cdtB and pltA were detected. [ABSTRACT FROM AUTHOR]

Microbiological surveillance of ready-to-eat (RTE) meat products provides empirical data to inform scientific guidance for improving food safety. In this study we conducted the first nation-wide survey of food-borne pathogens in RTE meat products in China in 2013. We analyzed the prevalence of food-borne pathogen in different product categories, market distribution, packaged forms, seasonal variation and regions. In total, 4047 samples were collected from all seven regions in China representing distinct geographical areas: Northern, Northeastern, Eastern, Central, Southern, Southwestern, and Northwestern Regions. Samples were collected from catering, retail, and wholesale sources in different seasons throughout the course of the year. The presence of Listeria monocytogenes, Salmonella spp. , Staphylococcus aureus and diarrheagenic Escherichia coli in all the samples was examined by China's national food safety standard method. All the surveillance data were analyzed according to meat product category, market distribution, packaged form, seasonal variation and regions, respectively. Microbial prevalence of L. monocytogenes, Salmonella spp., S . aureus and diarrheagenic E. coli were detected in 1.43% (57/3974), 0.64% (26/4035), 0.79% (32/4047) and 1.06% (40/3774), respectively. The prevalence of heat-treated category RTE meat products was high, probably due to cross contamination. Prevalence data for Salmonella spp. and S. aureus were higher in the third quarter of the year. We found packaging method played a consistent role in the prevalence of all four food-borne pathogens in packaged ready-to-eat meat products. Bulk ready-to-eat meat products were significantly more likely to contain contamination than portion packaged products. In all, this study implied a potential public health problem. It is necessary to improve control measures of RTE meat products. [ABSTRACT FROM AUTHOR]

Yersinia enterocolitica is an important food-borne enteropathogen that causes gastrointestinal syndromes. The aims of this study were to identify Y. enterocolitica in food samples in China, and to assess the pathogenic potential and antimicrobial resistance, and to characterize the genotypes of the isolates. From July 2011 to May 2014, a total of 2320 food samples were obtained, and 47 (2.03%) were found positive for Y. enterocolitica , while 706 retail-level ready-to-eat products and 249 vegetable samples were negative. A total of 58 Y. enterocolitica strains were isolated. All isolates belonged to biotype 1A, and the primary serotype was O:8. All strains lacked the ail , virF , ystA , and ystC virulence genes, but harbored the ystB , fepD , ymoA , fes , and sat genes. All 58 strains were sensitive to kanamycin and sulfonamide, but were resistant to two or more antibiotics. Most of the strains expressed the β-lactamase genes; the presence of blaA and blaB was detected in 97% and 100% of isolates, respectively. Many strains were resistant to trimethoprim/sulfamethoxazole (79.3%), ampicillin (91.4%), and cephalothin (91.4%). The 58 strains were grouped into three clusters and one singleton by enterobacterial repetitive intergenic consensus-polymerase chain reaction (ERIC-PCR) at a similarity coefficient of 70%, and each cluster was largely organized by geographical region. This study provides a valuable accounting of the prevalence of Y. enterocolitica from a nationwide survey of foods in China, and highlights the seasonal effects of Y. enterocolitica prevalence in foods in China for the first time. [ABSTRACT FROM AUTHOR]

Introduction: The etiological and clinical characteristics of patients with infectious diarrhea have changed during the last decade in Shanghai. Methodology: The records of 29,210 patients with infectious diarrhea in the outpatient department of the Jinshan Hospital (Shanghai, China) between January 1998 and December 2013 were analyzed. Results: A total of 2,849 samples were positive for intestinal pathogenic bacteria including Vibrio parahaemolyticus (2,489; 84.0%), Salmonella spp. (235; 8.3%), and Shigella spp. (125; 4.4%). V. parahaemolyticus infections are mainly characterized by abdominal pain, nausea, and vomiting, whereas Shigella spp. infections can, in addition, induce fever. In contrast, Salmonella infections can produce all of these symptoms but in a smaller percentage of patients. During the 16-year study, both the number of patients and the positive infection rate declined. Notably, the rate of infections by V. parahaemolyticus decreased while the detection rates of Salmonella spp. increased year by year from 2006 on with the introduction of a new detection method. Conclusions: Salmonella has been identified as the third-most frequent cause of diarrhea from 1998-2006, as the second-most frequent cause from 2006-2010, and as the most frequent cause from 2011-2013, which was mainly due to a sharp decrease of V. parahaemolyticus infections in 2011-2013. Salmonella strains collected in 2011-2013 showed high susceptibility to imipenem (100%) and meropenem (100%), whereas susceptibilities for ampicillin (39%) and piperacillin (40%) were low. [ABSTRACT FROM AUTHOR]

Vibrio parahaemolyticus is a major foodborne pathogen with a wide distribution in the world that causes economic and public health problems. Here, we isolated 152 V. parahaemolyticus strains from shellfish, shrimp, crab, and snails from 5 provinces in East China, and analyzed the genetic diversity, population structure, and virulence profiles of these isolates. Our results showed that the 152 V. parahaemolyticus strains belong to 84 different sequence types (STs), of which 69 (82.14 %) STs and 60 alleles were newly identified. The thermostable direct hemolysin (TDH) and the TDH-related hemolysin (TRH) were present in 4 V. parahaemolyticus isolates (2.63 %) respectively, while toxRS /new, a distinctive toxRS sequence that was associated with pandemic V. parahaemolyticus strains, is present in 52 isolates (34.21 %). Thereinto, both the ZJ11 and ZJ12 strains measure up to the standard of toxRS /new+, tdh +, and trh -, which was widely used marker for the rapid screening of pandemic strains, and thus these strains may have the risk of infectious outbreaks. In addition, we observed that all the 152 V. parahaemolyticus isolates encode type III secretion systems 1 and type VI secretion system (T6SS) 2, while 119 isolates (78.29 %) of them also contain T6SS1. The genetic relatedness of our isolates to the human V. parahaemolyticus collection was explored, which showed that ST6, ST79, ST162, ST1060, and ST1061 were all identified in both human isolates (7 isolates) uploaded in the PubMLST database and our marine products isolates (7 isolates). Our findings expand the views of the genetic diversity of V. parahaemolyticus and will contribute to understanding the potential risk of the transboundary spread of this bacterium. • 69 (82.14 %) STs of the 152 V. parahaemolyticus strains were newly identified. • Virulence genes tdh and trh were detected in 4 isolates (2.63 %) respectively. • The pandemic strains related gene toxRS /new is present in 52 isolates (34.21 %). • Some of the V. parahaemolyticus STs have a risk of transboundary spread to humans. [ABSTRACT FROM AUTHOR]

Salmonella is the most important foodborne pathogen in poultry production systems and can infect humans via consumption of contaminated food. Ducks, an important waterfowl widely raised in China, are also a vehicle that transmits Salmonella through the food supply chain. In this study, 701 samples were collected from each production stage of the duck production chain. Salmonella was isolated and identified, and the isolates were tested for drug sensitivity and molecular typing based on whole genome sequencing (WGS) to explore the prevalence of Salmonella in the duck production chain. Altogether, a total of 180 Salmonella isolates (25.7%) were obtained from the duck production chain, 82 (35.7%) isolates were from hatchery samples, followed by 64 (29.2%) from market samples, 17 (23.6%) from farm samples, and 17 (9.4%) from slaughterhouse samples. All isolates were divided into 9 serotypes, among which S. Typhimurium, S. Anatum, and S. Enteritidis were the dominant serotypes. The S. Typhimurium was distributed in various production stages in the duck production chain. Among the 16 antibiotics, selected 60 isolates were only resistant to NAL, indicating that resistance of Salmonella in the duck production chain was low. WGS phylogenetic relationship results based on core-genome SNPs showed that S. Typhimurium can spread across geographic regions and along between different stages of the duck production chain, eventually reaching the market where it is a potential threat to consumer health. This study explored the prevalence of Salmonella in the duck production chain which will provide data support for proposing some interventions to control Salmonella. [ABSTRACT FROM AUTHOR]

Salmonella enterica subsp. enterica serovar ,4,[5],12:i:- is a monophasic variant of Salmonella Typhimurium, which has recently been recognized as an emerging cause of infection worldwide. This bacterium has also ranked among the four most frequent serovars causing human salmonellosis in China. However, there are no reports on its contamination in Chinese food. Serotyping, polymerase chain reaction, antibiotic resistance, virulotyping, and multilocus sequence typing (MLST) assays were used to investigate the prevalence of this serological variant in food products in China, and to determine phenotypic and genotypic difference of monophasic isolates and Salmonella Typhimurium isolated over the same period. Salmonella ,4,[5],12:i:- was prevalent in various food sources, including beef, pork, chicken, and pigeon. The study also confirmed the high prevalence (53.8%) of resistance to ampicillin, streptomycin, sulfonamides, and tetracycline in Salmonella ,4,[5],12:i:-, which was higher than that in Salmonella Typhimurium. Moreover, Salmonella ,4,[5],12:i:- isolates in our study were different from Salmonella Typhimurium isolates by the absence of three plasmid-borne genes (spvC, pefA, and rck) and the presence of gipA in all isolates. All Salmonella ,4,[5],12:i:- isolates demonstrated MLST pattern ST34. Genomic deletions within the fljBA operon and surrounding genes were only found in Salmonella ,4,[5],12:i:- isolates, with all isolates containing a deletion of fljB. However, hin and iroB were identified in all Salmonella ,4,[5],12:i:- isolates. Three different deletion profiles were observed and two of them were different from the reported Salmonella ,4,[5],12:i:- clones from Spain, America, and Italy, which provided some new evidence on the independent evolution of the multiple successful monophasic clones from Salmonella Typhimurium ancestors. This study is the first report of Salmonella ,4,[5],12:i:- in food products from China. The data are more comprehensive and representative, providing valuable information for epidemiological studies, risk management, and public health strategies. [ABSTRACT FROM AUTHOR]

Vibrio parahaemolyticus is one of the most common foodborne pathogens in Asian countries. V. parahaemolyticus contamination of retail shrimp in China has been reported previously, and such contaminated shrimp have been linked to outbreaks of foodborne diseases. However, to date, the prevalence of V. parahaemolyticus in retail shrimp in China has not been determined. This study aimed at identifying the prevalence of V. parahaemolyticus in shrimps in Chinese retail market. From May 2012 to April 2013, a total of 273 shrimp samples was obtained from retail markets in 16 provinces (19 cities) of China. V. parahaemolyticus was detected in 103 (37.7%) of 273 samples by the most probable number method. Bacterial densities were less than 100 MPN/g in 95.1% (98/103) of the samples. Five trh-positive isolates were identified from 247 isolates, and none of the isolates were tdh-positive. In multiplex PCR-based O-antigen serotyping of these 247 pathogenic isolates, all O-antigen serotypes, except O9, were detected, and serotype O2 was found to be the most prevalent (detected in 82 isolates). This is the first report on V. parahaemolyticus prevalence in retail shrimp in China, and the findings of this study can be used for microbiological risk assessment of shrimp in China. [ABSTRACT FROM AUTHOR]

The massive food wastes pose a growing health concern for spreading of antibiotic resistance and pathogens due to food spoilage. However, little is known about these microbial hazards during collection, classification, and transportation before eventual treatment. Here, we profiled the temporal variations of antibiotic resistance genes (ARGs), pathogens, bacterial and fungal communities across four typical food wastes (vegetable, fish, meat, and rice) during storage at room temperature in summer (maximum 28–29 °C) of typical southeast city in China. A total of 171 ARGs and 32 mobile genetic elements were detected, and the absolute abundance of ARGs significantly increased by up to 126-fold with the storage time. Additionally, five bacterial pathogens containing virulence factor genes were detected, and Klebsiella pneumoniae was persistently detected throughout the storage time in all food types except rice. Moreover, fungal pathogens (e.g., Aspergillus , Penicillium , and Fusarium) were also frequently detected. Notably, animal food wastes were demonstrated to harbor higher abundance of ARGs and more types of pathogens, indicating a higher level of hazard. Mobile genetic elements and food types were demonstrated to mainly impact ARG profiles and pathogens, respectively. This work provides a comprehensive understanding of the microbial hazards associated with food waste recycling, and will contribute to optimize the food waste management to ensure biosecurity and benefit human health. [Display omitted] • A total of 171 ARGs and 32 MGEs were detected in spoiled food wastes. • Five bacterial pathogens and several potential mycotoxigenic fungi accumulated. • The ARG absolute abundances significantly increased during food waste spoilage. • Fish harbored the highest abundances of ARGs and pathogens. • MGEs and food types mainly impacted the ARG profiles and pathogens, respectively. [ABSTRACT FROM AUTHOR]

Listeria monocytogenes is an important foodborne pathogen worldwide, with 20–30% fatality rate in vulnerable persons. The hypervirulent L. monocytogenes clonal complex (CC) 87 strains have emerging both in food production environments and clinic cases. The objective of this study was to develop a multiplex PCR to simultaneously detect L. monocytogenes CC87 and CC88 strains based on pan-genome analysis. A novel multiplex PCR comprised of genes A6K41_13255 (specific for CC87 and 88) , BCW_4260_01987 group_8135 (specific for CC88) and 02-1103_01073 group_5869 (specific for L. monocytogenes) were designed. The specificity of this multiplex PCR was robust verified with other CCs of L. monocytogenes and other species strains. The detection limit of this multiplex PCR for CC87 and CC88 were 1.7 × 104 cfu/mL and 2.1 × 104 cfu/mL, respectively. This multiplex PCR could accurately detect CC87 and CC88 strains with the interference of different ratios of L. monocytogenes CC8, CC9, CC121, CC155, and L. innocua strains. Furthermore, this multiplex PCR method could successfully detect 1.9 × 104 cfu/mL of L. monocytogenes CC87 and 1.7 × 104 cfu/mL CC88 strains in artificially contaminated milk after 9 h enrichment, respectively. In addition, this multiplex PCR could accurately detect CC87 isolates in food samples within 48 h, which was faster than the routine MLST analysis. In conclusion, this novel multiplex PCR offers a promising approach for accurate, inexpensive, and rapid detection of L. monocytogenes CC87 and CC88 strains simultaneously, which could apply to surveillance the prevalence of CC87 and CC88 strains in both food and food production environments and to evaluate the effect of disinfection measures for controlling the persistent L. monocytogenes contamination. • Comparative genome analysis was performed for 673 Listeria monocytogenes strains. • A multiplex PCR was developed for simultaneous identification Listeria monocytogenes CC87 and 88 strains. • This novel method is specific, sensitive, economical, and had a run-time within 48 h. • Rapid screening of L. monocytogenes sequence CC87 and 88 strains in food items is possible. [ABSTRACT FROM AUTHOR]

Objectives Listeria is an important foodborne pathogen with severe manifestations and high case-fatality rate. However, listeriosis is not yet a notifiable disease in China, and there is no national monitoring system for cases. We conducted a systematic review to better understand the clinical and epidemiologic features of listeriosis in China. Methods Both electronic and manual retrieval systems were used to search Chinese literature for cases and isolates of human listeriosis reported between 1964 and 2010. We recorded and analysed demographic, clinical and laboratory information available for reported cases. Results A total of 147 clinical cases, 479 Listeria isolates and 82 outbreak-related cases were reported in 28 (90%) provinces in China from January 1964 to December 2010. Of the clinical cases, 45 (31%) were central nervous system infections, 68 (46%) were septicaemia and 34 (23%) were focal infections or gastroenteritis. The overall case-fatality rate was 26% (34/130) among clinical cases with known outcomes and 46% (21/46) among neonatal cases. Conclusion Listeriosis cases occurred in China throughout the study period between 1964 and 2010. Case-fatality was similar to published data from other countries. China should consider requiring notification of listeriosis cases to improve estimates of incidence, identification of risk factors and design of preventive measures. [ABSTRACT FROM AUTHOR]

Abstract: Milk of dairy cows can harbor a variety of microorganisms including Listeria monocytogenes, the first to be identified as an important foodborne pathogen. This pilot survey aimed to assess the presence of L. monocytogenes in raw whole milk in 15 provinces of China between June 2009 and October 2010. All 5211 analyzed samples were compliant using polymerase chain reaction (PCR) detection. A total of 19 samples were positive in 9 provinces, while no PCR-positive samples were obtained in the other 6 provinces. The prevalence of L. monocytogenes in raw milk was 0.36% in the 15 Chinese provinces, while the prevalence of positive areas within these dates was 0.23–1.2% among the nine provinces. Among the investigated 24 herds, rates of L. monocytogenes positivity were 0.17–2.89% in 13 herds, whereas they were 0% in the other 11 herds. There was a significant difference (p < 0.05) in PCR-positive data between organized farms (0.19%) and private herds (1.83%). These results indicate that there is a lower risk of contamination in the milking process in China when more attention is paid to maintaining good milking and strict hygiene practices, especially in private herds. [Copyright &y& Elsevier]

Five hundred fifty samples were collected from five chicken farms in Shanghai during March 2005 to October 2006. Twenty-five samples tested positive for Salmonella from a total of 550 samples, of which 500 were obtained from feces of healthy chickens and 50 were obtained from diseased chicks. The 25 presumptive Salmonella isolates were confirmed by the API 20E identification kit. Serotyping of these isolates by agglutination tests with antiserum displayed seven serovars; genotyping of these isolates with multilocus sequence typing demonstrated six sequence type (ST) patterns (i.e., ST-11, ST-19, ST-92, ST-96, ST-290, and ST-367). The multilocus sequence typing data revealed that some of these strains, isolated from different farms, might have the same ST and might come from the same source. The susceptibilities of these strains to 14 antimicrobials were determined; most of the isolates (13 of 25) were-resistant to doxycycline and tetracycline and two isolates Were resistant to cefotaxime and ceftazidime, but none was resistant to gentamicin or kanamycin. [ABSTRACT FROM AUTHOR]

Objective: To investigate the occurrence of important foodborne pathogens in shellstock Pacific oysters in the food markets in South China. Methods: From July 2007 to June 2008, retail oysters were collected in different seasons from South China and analyzed for the prevalence and levels of Listeria monocytogenes, Vibrio vulnificus and Vibrio parahaemolyticus. Results: None of L. monocytogenes could be detected in any of the 202 oyster samples tested, while V. vulnificus and V. parahaemolyticus could be detected in 67 (54.9%) and 109 (89.3%) of the 122 oyster samples analyzed, respectively, with an MPN (most probable number) value greater than or equal to 3. V. vulnificus and V. parahaemolyticus with a more than 102 MPN/g were found in 36 (29.5%) and 59 (48.4%) of the 122 oyster samples, respectively. The tdh and trh genes were detected in 4 (0.3%) and 8 (0.6%) of the 1 349 V. parahaemolyticus isolates, respectively. Of the 122 samples, 4 (3.3%) was positive for either tdh or trh. The levels of V. vulnificus and total V. parahaemolyticus in oysters in South China varied in different seasons. Conclusion: V. vulnificus and pathogenic V. parahaemolyticus are frequently found in oysters in south China, which may pose a potential threat to public health. Data presented here will be useful for the microbiological risk assessment in oysters in China. [Copyright &y& Elsevier]