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The degree of contamination of retail meat with colistin-resistant bacteria and its potential contribution to dissemination within communities remains to be determined. Thus, we aimed to elucidate the contamination status of colistin-resistance genes, indicative of colistin-resistant bacteria, in retail meats in Vietnam. In total, 46 chicken and 49 pork meats from stores in Vietnam and Japan were examined. Multiplex real-time polymerase chain reaction with TaqMan probes was performed for detecting mcr-1 , mcr-3 , and Escherichia coli 16S rRNA . Colistin-resistant bacteria in meats were isolated using selective media. The minimum inhibitory concentrations of colistin were determined using the broth microdilution method. The results showed that 70.7% of chicken meats in Vietnam were contaminated with both mcr-1 and mcr-3 . Meanwhile, mcr-1 and mcr-3 were detected in 15.9% and 40.9% of pork meat, respectively. Only mcr-3 was detected in 40% of chicken in Japan. In addition, mcr-1 -harboring E. coli and mcr-3 -harboring Aeromonas were isolated from chicken meats in Vietnam. Some of these isolates showed colistin resistance. These results showed that most retail meats were highly contaminated with colistin-resistance genes. Notably, our results suggest that mcr-3 is more prevalent in the contaminated samples compared with mcr-1 .

The pork production chain is an important reservoir of antimicrobial resistant bacteria. This study identified and characterized integrons in Salmonella isolates from a Brazilian pork production chain and associate them with their antibiotic resistance pattern. A total of 41 whole-genome sequencing data of nontyphoidal Salmonella were analyzed using PlasmidSPAdes and IntegronFinder software. Nine isolates (21.9%) had some integrons identified (complete and/or incomplete). Six complete class 1 integrons were found, with streptomycin resistance genes ( aadA1 , aadA2 ) alone or downstream of a trimethoprim resistance gene ( dfrA1 , dfrA12) , and some also containing resistance genes for sulfonamides ( sul1 , sul3 ) and chloramphenicol ( cmlA1 ). Class 2 integron was detected in only one isolate, containing dfrA1 - sat2 - aadA1 gene cassettes. Five isolates harbored CALINs-clusters attC but lacking integrases-with antimicrobial resistance genes typically found in integron structures. In all, integrons were observed among four serotypes: Derby, Bredeney, Panama, and monophasic var. Typhimurium I 4,[5],12:i:-. The association of integrons with antibiotic resistance phenotype showed that these elements were predominantly identified in multidrug resistance isolates, and six of the seven gentamicin-resistant isolates had integrons. So, surveillance of integrons in Salmonella should be performed to identify the potential for the spread of antimicrobial resistance genes among bacteria.

Antimicrobial resistance (AMR) is a recognized global public health concern. Although the link between antimicrobial usage in food animals and AMR in humans is established, the detailed interactions are unclear. Antimicrobial stewardship (AMS) in livestock was first implemented in Europe with Sweden as the pioneer in 1986. Despite this head start, AMR is still an ongoing challenge for Europe. The European Union (EU) is an established agriculture producer, the second largest pork producer globally, and one of the largest markets for organic food. China is the global leader in both production and consumption of pork. China's rise in prosperity has led to an increase in its pork demand. Chinese producers commonly use antimicrobials during production for disease treatment and prevention to meet this increased demand. China's rising prosperity together with recent publicized food safety scandals, disease outbreaks in domestic livestock products, and increased AMR awareness have resulted in an increased willingness to pay and demand for organic food by Chinese consumers. Responding to the growing concerns of AMR by consumers and the World Health Organization (WHO), the Chinese government introduced a national pilot program in 2016 to reduce unnecessary antimicrobial use. Compared with China, the EU is a different entity as it is a political union comprising diverse countries and although it may have more experience in AMS, both entities face similar issues with AMR and increasing demand for organic food. Increased interest in organic food has arisen due to concerns about AMR, food safety, outbreaks of bacterial food contamination, and animal welfare. This article aims to compare the different AMS strategies employed by each entity, China and the EU, and how the increased demand for organic produce globally also influences the effort to reduce antimicrobial use in these entities' pork industries.

One objective of this study was to determine overall prevalence of Salmonella in ground pork from U.S. retail stores over three seasons including both case-ready and store-ground packages. Package types collected included: overwrap, chub, modified atmosphere packaging, and other (plastic or wax paper wrapped). Because package type represents different production systems and are subject to varied microbiological government regulation and testing methodologies, both USDA-FSIS and FDA Salmonella isolation protocols were performed. Another objective of the study was to determine serotypes and antimicrobial susceptibility profiles of the isolates obtained from the ground pork samples. Ground pork aliquots were subjected to real-time PCR. Recovered isolates were serotyped and minimum inhibitory concentration analysis to 15 antimicrobials was determined using microbroth dilution. Overall prevalence of Salmonella in ground pork from the 865 samples collected was 1.39%. Prevalence was not affected by package type ( p  = 0.29) nor grind location (case-ready vs. store-ground; p  = 0.17). Season affected Salmonella prevalence ( p  = 0.05) with most isolates found during fall, and there was a tendency for geographic region to affect prevalence ( p  = 0.07). The USDA Salmonella isolation method was more effective at recovering isolates ( p  = 0.01) compared with the FDA methodology and yielded a kappa statistic of 0.26 as a measure of agreement. The serotypes isolated included: Infantis, 4,5,12:i:-, Brandenburg, Typhimurium var 5-, Seftenberg, and Johannesburg with only two packages containing multiple serotypes. No isolates were resistant to antibiotics commonly used to treat human Salmonella infections including extended spectrum cephalosporins or fluoroquinolones. Although the recovery of Salmonella from retail ground pork samples was rare, Salmonella Typhimurium (and its monophasic variant 4,5,12:i:-), which are among the most common serovars recovered from human infections, were recovered. Therefore, more effective strategies to further reduce or eliminate these pathogens from retail pork products are warranted.

This study was designed to investigate the prevalence and characteristics of Salmonella in three Chinese pig abattoirs (A, B, and C) in Wuhan city in 2016. Four types of pig samples were collected and cultured for Salmonella . Salmonella was detected from 329 samples among the 1440 tested (22.9%). There was no significant difference in the overall prevalence between the first visit and the second visit and among the three abattoirs. Rectal swabs (RS) exhibited a significantly higher prevalence than carcass swabs and pork. A total of 177 isolates were characterized by multilocus sequence typing, serotyping, and antimicrobial susceptibility testing. Among 17 sequence types (STs) and 13 serotypes detected, ST40, ST469, and ST34, corresponding to serovars Derby, Rissen, and Typhimurium, respectively, were predominant. The isolates from different abattoirs exhibited diverse ST distribution. The minimum inhibitory concentrations were determined using the microdilution broth method. Resistance to at least one of the antimicrobials was observed for 96.6% of the strains (171/177), and multidrug resistant (MDR) isolates accounted for 75.7% of the strains (134/177). The highest resistance proportion was for tetracycline (92.7%), and the lowest was for cefotaxime (14.1%). The isolates from abattoir A exhibited a significantly lower MDR proportion than those from other abattoirs ( p  < 0.05). The isolates recovered from RS and pork samples exhibited significantly higher MDR proportions than those recovered from carcass swab samples. Notably, among three predominant STs of isolates, the ST34 isolates showed the highest MDR proportion. In view of the high Salmonella prevalence and antimicrobial resistance, great attention must be paid to the monitoring and controlling of Salmonella in a full pork production chain.

Shiga toxin-producing Escherichia coli (STEC) strains are important food-borne pathogens that can be transmitted through the consumption of food products derived from pigs. Moreover, antimicrobial resistance in STEC has been a matter of increasing concern. The aim of this study was to investigate the prevalence and antimicrobial characteristics of STEC isolates from pork in Korea. We isolated 131 isolates of E. coli from 334 pork samples collected from slaughterhouses and retail markets from 2008 to 2009. Among the 131 isolates, 6 (4.58%) were confirmed to belong to 6 different serotypes of STEC. All six STEC isolates contained stx1 and eaeA virulence genes, and four of them additionally carried the hly gene. The minimum inhibitory concentration (MIC) of 15 antibiotics (amoxicillin/clavulanic acid, ampicillin, cephalothin, cefoxitin, ceftiofur, gentamicin, neomycin, streptomycin, nalidixic acid, ciprofloxacin, colistin, chloramphenicol, florfenicol, tetracycline and sulfamethoxazole/trimethoprim) toward the STEC isolates was determined. As a result, three strains were associated with high MICs for florfenicol and chloramphenicol (64 μg/mL). Furthermore, all three strains were found to contain the florfenicol-resistant gene ( floR ) but not the chloramphenicol-resistant gene ( cat ). Sequence alignment and BLAST analysis of the polymerase chain reaction products of the floR gene indicated that they contained sequences with homology to the floR gene of E. coli or Salmonella enterica serovar, Heidelberg. This is the first report on the detection of floR in STEC isolated from pork obtained from retail markets in Korea.

The mcr-1 gene has been identified in bacterial isolates obtained from humans, animals, environment, and food, including Salmonella spp., which is one of the major foodborne pathogens worldwide. The aim of this study was to evaluate the presence of mcr-1 gene in Salmonella spp. from food produced in Brazil and to characterize the isolates harboring this gene. A total of 490 Salmonella spp. isolates from the Brazilian National Program for the Control of Foodborne Pathogens were screened for the presence of mcr-1 gene by polymerase chain reaction (PCR). Whole genome sequencing (WGS) was performed in positive isolates to characterize the sequence type (ST), plasmid families and resistance genes. Antimicrobial susceptibility tests were performed by broth microdilution. Selected isolates were submitted to conjugation experiments using the Escherichia coli J53 as a receptor. We detected eight isolates harboring the mcr-1 gene; seven belonged to Salmonella enterica serovar Typhimurium and its monophasic variant 4,[5],12:i:-, and one belonged to serovar Saintpaul. Seven of the mcr-1 positive isolates displayed a high rate of resistance to other antibiotics in addition to colistin. Analysis of the WGS indicated that the ST 19 was the most common ST among the mcr-1 positive isolates. The mcr-1 gene was located in an IncX4 plasmid of ∼33 kb, with no additional resistance genes and with high identity with a plasmid obtained from a clinical isolate of E. coli mcr-1 positive in Brazil. All plasmids harboring the mcr-1 gene were able to conjugate. Our results suggest the spread of a single plasmid type in Brazil harboring the mcr-1 among Salmonella spp. The horizontal transfer of this mobile element has been contributing to the spread of the colistin resistance in the country.

This study assessed an enzyme-linked immunosorbent assay (ELISA) based assay to detect Salmonella in swine as a potential tool to predict the presence of Salmonella in swine carcasses. The following samples were collected from 10 swine batches: blood ( n  = 100); environment (barn floor, n  = 10, and lairage floor, n  = 10); meat juice ( n  = 100, obtained after defrosting of diaphragm); tonsils ( n  = 100); mesenteric lymph nodes (MLNs) ( n  = 100); and carcasses after bleeding ( n  = 100), after singeing ( n  = 100), after evisceration ( n  = 100), and after final rinsing ( n  = 100). Blood and meat juice were subjected to ELISA to detect antibodies against Salmonella , and other samples were subjected to Salmonella detection by ISO 6579. Salmonella was detected in 3 samples from barn floors, 7 lairage floors, 45 tonsils, 43 MLNs and in 3 carcasses. Based on ELISA, Salmonella positive samples were: 86 and 46 blood serum (20% and 40% cut-offs) and 68 and 46 meat juice (20% and 40% cut-offs). Optical density readings from blood serum and meat juice presented a high and significant correlation ( r  = 0.93, p  < 0.001), and a substantial agreement for Salmonella detection ( K  = 0.69, ELISA 40% cut-off). The agreement between ELISA and microbiological analysis for Salmonella detection in pig carcasses were absent or poor, with the exception of results obtained by ELISA 40% cut-off from blood serum and meat juice with MLNs ( K  = 0.49 and 0.50, respectively) and tonsils ( K  = 0.29 and 0.30, respectively). Based on the obtained results, meat juice can be considered an alternative to blood serum as a matrix for ELISA for preliminary detection of Salmonella , allowing the identification of potential sources of contamination during slaughtering.