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Salmonella Enteritidis is an important foodborne pathogen with high prevalence of resistance to cephalosporins, imposing a serious threat to public health. Therefore, a total of 162 Salmonella Ente...

In this study, we explored the prevalence of oxacillin-susceptible mecA-positive Staphylococcus aureus (OS-MRSA) in staphylococcal food poisoning outbreak isolates and foodborne isolates, and then investigated their molecular characteristics, classical staphylococcal enterotoxins (SEs), and drug resistance. Eight (2.9%) of 275 isolates from food poisoning outbreaks and 7 (3.8%) of 184 isolates from retail foods were identified as OS-MRSA isolates. Among the 15 OS-MRSA isolates, the most frequently detected toxin genes were hld (100%), hla (93.3%), pvl (80.0%), and hlb (46.7%) followed by seg and seq (33.3%, each), hlg (26.7%), seb and hlgv (20.0%, each), sec, seh, sel, sep, and tst (13.3%, each), and sei, sem, sen, and seo (6.7%, each). None of isolates carried other tested virulence genes. The most frequently detected classical SEs were SEB and SEC (26.7%, each), followed by SEA and SEE (20.0%, each), and SED (6.7%). Resistance was most frequently observed in ampicillin, penicillin, and cefoxitin (100%, each), followed by trimethoprim/sulfamethoxazole (93.3%), erythromycin (73.3%), amoxicillin/clavulanic acid (46.7%), tetracyclines (26.7%), and ciprofloxacin (6.7%). All isolates were susceptible to other tested antibiotics. A dominant molecular type belonged to ST398-IVa-t034 (26.7%), followed by ST59-IVa-t437 (20.0%), ST88-III-t14340 and ST1-IVa-t114 (13.3%, each), and ST5-II-t002, ST630-t4549, ST5-II, and ST4495-t10738 (6.7%, each). Our findings indicated that OS-MRSA strains had a low prevalence rate among outbreak strains and foodborne strains, which frequently harbored SCCmec IVa, and carried a variety of toxin genes, and also expressed numerous classical SEs. In addition, all OS-MRSA isolates were susceptible to the majority of antibacterial agents except β-lactam. Our study is the first to report that OS-MRSA isolates are associated with food poisoning outbreaks worldwide.

In this study, we explored the prevalence of oxacillin-susceptible

Salmonella producing β-lactamases has spread rapidly worldwide and poses a serious threat to human and animal health. In this study, we characterized 220 ceftriaxone (CRO)-resistant isolates identified among 3153 Salmonella from humans, animals, food, and water collected in Shanghai, China. They were assessed for antimicrobial susceptibility, phenotypic identification of extended-spectrum β-lactamases (ESBLs), and β-lactamase genes and integrons. CRO resistance in Salmonella increased from 5.0% in 2011 to 8.4% in 2013. Salmonella Enteritidis (45.5%), Salmonella Typhimurium (20.9%) from humans, and Salmonella Indiana (14.5%) from poultry represented the majority of the CRO-resistant isolates. Many isolates were also resistant to other antimicrobials, including nalidixic acid (84.5%), sulfisoxazole (70.5%), and tetracycline (61.8%). Resistance to ciprofloxacin was also found in 33.6% of the isolates. Most isolates (98.2%) were confirmed as ESBL producers. Resistance genes such as blaCTX-M, blaTEM, and blaOXA were detected in 207 (94.1%), 99 (45%), and 53 (24.1%) isolates, respectively. Three types of integron I and one type of integron II were identified in 13 (5.9%) and 2 (0.9%) isolates, respectively. The integrons encompassed 10 different genes: dfrA1/12/17/25, aadA1/2/5, sat2, orfF, and ybeA. Our study underscores concern for increasing CRO resistance, and highlights the widespread ESBL genes in Salmonella enterica.

We characterized antibiotic resistance profiles, antibiotic resistance-associated genes, and pulsed-field gel electrophoresis (PFGE) patterns of 145 Salmonella enterica serotype Typhimurium isolates from human infections and retail foods that were possibly responsible for salmonellosis outbreaks from 2008 to 2012 in Shanghai, China. Resistance to at least three antibiotics was found in 66.7% of chicken isolates, 76.5% of duck isolates, 77.8% of pork isolates, and 80.5% of human isolates. Seven antibiotic resistance phenotypes were detected in chicken isolates, 16 in pork isolates, 17 in duck isolates, and 50 in human isolates. No significant difference (p 0.05) was found between Salmonella isolates derived from human salmonellosis and from retail foods in terms of the percent resistance of ampicillin, amoxicillin/clavulanic acid, ceftiofur, ceftriaxone, nalidixic acid, chloramphenicol, gentamicin, kanamycin, streptomycin, tetracycline, sulfisoxazole, and sulfamethoxazole/trimethoprim. PFGE using XbaI and BlnI showed that some Salmonella isolates recovered from human infections and retail foods had same or highly similar genetic profile. Same or similar antibiotic resistance profiles, antibiotic resistance associated genes (i.e., qnrA, qnrB, qnrS, aac(6')-Ib, and oqxAB), gene cassettes (i.e., aadA2, dfrA12-aadA2, and aadA1), and mutations were detected in those isolates that exhibited high genetic similarities. These findings highlighted the frequent presence of Salmonella Typhimurium in retail chicken, pork, duck, and humans.

Salmonella enterica serotype Derby is among the three most common serotypes of nontyphoidal Salmonella isolated from patients with diarrhea in China. In this study, 133 Salmonella Derby isolates from human patients (n = 74) and foods of animal origin (n = 59) in Shanghai, China, between September 2013 and December 2014, were selected to study its phenotypic characteristics and genetic diversity. The isolates were subjected to antimicrobial susceptibility testing, plasmid replicon typing, virulence profile determination, and molecular subtyping by pulsed-field gel electrophoresis (PFGE). Isolates were frequently resistant to tetracycline (87.22%), sulfisoxazole (74.44%), and streptomycin (62.41%), and a low frequency of resistance was found toward ofloxacin (3.01%), ceftazidime (2.26%), and cefepime (1.50%); in addition, 93 (69.92%) isolates were multidrug resistant. The most common plasmid incompatibility replicon types were the IncF family (FIA, 51.31%; FIC, 27.82%; and FIB, 21.80%) and IncP types (35.34%): these plasmid types may be associated with the spread of antibiotic resistance and virulence genes. All isolates were positive for the Salmonella pathogenicity island (SPI) gene avrA and the fimbrial gene bcfC from among the 10 virulence genes detected, and most of them carried ssaQ (99.25%), mgtC (97.74%), siiD (98.50%), sopB (97.74%), and sopE (96.99%). PFGE showed 68 patterns in nine main clusters at an 85% similarity threshold. Most of the isolates from different sources possessed the same fingerprints or molecular profiles in each cluster, which strongly suggests the possibility that foods of animal origin, especially pork, serve as an important source for human infection. Moreover, this diversity may suggest strains originating from multiple clones. Therefore, surveillance on this serotype should be strengthened to prevent transmission of Salmonella Derby from foods of animal origin, especially pork, to humans.

This study aimed to trace the transmission source of Salmonella enterica serovar Typhimurium and Salmonella enterica serovar Enteritidis strains associated with enteric infections in Shanghainese children, and understand the molecular mechanism of resistance to third-generation cephalosporins and ciprofloxacin.The profiles of pulsed-field gel electrophoresis (PFGE) were compared among the isolates from children, animal, and environment. Antimicrobial susceptibility was determined using the minimal inhibitory concentrations and Kirby-Bauer disk diffusion method. Extended-spectrum β-lactamase (ESBL) producing isolates mediated by resistance genes were identified using polymerase chain reaction and sequencing.Based on PFGE patterns, 49 (33.1%) of 148 human Salmonella Typhimurium isolates located in the dominant PFGE clusters were genetically related to the isolates from poultry source, environment water, aquatic products, and reptiles, whereas 97 (97.0%) of 100 human Salmonella Enteritidis isolates were genetically related to isolates from poultry and water. The rates of resistance to ceftriaxone among clinical Salmonella Typhimurium and Salmonella Enteritidis isolates were 42.0% and 14.2%, respectively. Besides, 35.1% of Salmonella Typhimurium isolates displayed resistance to ciprofloxacin; 64.9% of Salmonella Typhimurium isolates and 97.0% of Salmonella Enteritidis isolates displayed reduced susceptibility to ciprofloxacin. Of 64 ESBL/AmpC-producing strains, CTX-M, TEM, DHA, and CMY were detected at frequencies of 86.0%, 62.5%, 7.8%, 3.1%, and 3.1%, respectively.The transmission sources of Salmonella Typhimurium and Salmonella Enteritidis infections in Shanghainese children were diverse. The high prevalence of resistance to third-generation cephalosporins and ciprofloxacin mediated by multiple molecular mechanisms needs continuous monitoring and intervention.

Salmonella enterica serovar Enteritidis is the leading global cause of salmonellosis. A total of 146 Salmonella Enteritidis isolates obtained from retail chicken products in Shanghai, China were characterized for their antimicrobial susceptibilities, virulence and antibiotic resistance gene profiles, and molecular subtypes using pulsed-field gel electrophoresis (PFGE). Approximately 42% (61/146) of the isolates were susceptible to all 13 antimicrobials tested. More than half of the isolates (50.70%) were resistant to ampicillin, 49.32% to sulfisoxazole, 17.12% to tetracycline, and 15.75% to doxycycline. Thirty (20.55%) isolates were resistant to three or more antimicrobials. The avrA, mgtC, and sopE virulence genes were identified in all isolates, while 97.2% and 92.4% were positive for bcfC and spvC genes, respectively. Genes associated with resistance to streptomycin (aadA), β-lactams (blaTEM, blaCMY, blaSHV, and blaCTX), tetracycline (tetA and tetB), and sulfonamides (sulI, sulII, and sulIII) were detected among corresponding resistant isolates. A total of 41 PFGE patterns were identified from 77 antimicrobial resistance (AMR) isolates and were primarily grouped into seven clusters (A-G), each with 90% similarity. The majority of Salmonella Enteritidis isolates (63.63%, 49/77) shared the same PFGE cluster, indicating potential cross contamination during processing and cutting or working during retailing and marketing. A significantly (p 0.05) lower percentage (25%) of isolates belonging to clusters D and E were resistant to sulfisoxazole compared with those belonging to clusters A, B, C, F, and G (80%), indicating that sulfisoxazole resistance might be associated with genetic content (PFGE profiles) of Salmonella Enteritidis. This study provides important and updated information about the baseline antimicrobial-resistant data for food safety risk assessment of Salmonella Enteritidis from retailed chicken in Shanghai, which is the first step for the development and implementation of China's AMR National Action Plan, and can be helpful for future surveillance activities to ensure the safety of the chicken supply.

Salmonella enterica serovar Stanley is an important serovar that has been increasingly identified in human salmonellosis. The present study aimed to investigate the antimicrobial resistance and molecular typing of 88 Salmonella Stanley strains isolated from humans (diarrhea patients, n = 64; and healthy carrier, n = 1), foods (aquatic products, n = 16; vegetable, n = 1; and pork, n = 1), and environment (waste water, n = 2; and river water, n = 3) in Shanghai, China from 2006 to 2012. Nearly half of the strains were resistant to sulfafurazole (43/88, 48.9%), and many were resistant to streptomycin (35/88, 39.8%), tetracycline (22/88, 25%), and nalidixic acid (19/88, 21.6%). Approximately a quarter of the strains (24/88, 27.3%) were resistant to more than three antimicrobials, and five had ACSSuT resistance type. Six clusters (A-F) were identified by pulsed-field gel electrophoresis (PFGE) with 80% similarity. Interestingly, strains in the same cluster identified by PFGE possessed similar antibiotic resistance patterns. PFGE typing also indicated that aquatic products might serve as a transmission reservoir for Salmonella Stanley infections in humans.

Terrapins and turtles are known to transmit Salmonella to humans. However, little was known about the occurrence of this pathogen in soft-shelled terrapin that is a popular delicacy in Chinese and other East Asian cuisines. We isolated and characterized 82 (24.4%) isolates of Salmonella from 336 fecal samples of soft-shelled terrapins (51 of 172; 29.7%) and pet turtles (31 of 164; 18.9%) in Shanghai. Salmonella Thompson was the most common serotype (17.1%) among others. Many isolates (84.1%) were resistant to multiple antimicrobials (≥3). Molecular analysis of Salmonella Thompson and Salmonella Typhimurium using pulsed-field gel electrophoresis unveiled a close genetic relationship between several human and terrapin isolates. Our results highlight the risk associated with the handling and consumption of turtles and their role in the spread of Salmonella in the human salmonellosis.

Salmonella enterica serotype Agona (Salmonella Agona) has been among the top 10 serotypes that cause human diarrheal diseases in China. A total of 95 Salmonella Agona (67 from humans, and 28 from animals, food of animal origins, and environmental sources) recovered in Shanghai, China from 2005 to 2011 were subjected to antimicrobial susceptibility testing and molecular subtyping using pulsed-field gel electrophoresis (PFGE). Approximately 68.4% of the Salmonella Agona isolates were pansusceptible to 15 antimicrobial agents tested, and 4 isolates (4.21%) were resistant to at least 3 antimicrobials. PFGE analysis resulted in 41 unique patterns, of which 4 major PFGE patterns (X3, X4, X5, and X6) were grouped together at 96.1% similarity. Isolates of the four patterns included those from food (pork, beef, and chicken) and humans. Our findings showed that the same clones of Salmonella Agona were recovered from human patients and food, and that food of animal origin was potentially a major vehicle of Salmonella Agona in human salmonellosis in Shanghai.