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Aims To assess the co-transmission risk of phenotypic and genetic resistance to cephalosporins, colistin, and fosfomycin in Salmonella strains collected along the whole pork production chain. Methods and Results From a total of 107 Salmonella isolates from samples collected in pig slaughterhouses and markets, 15 ESBL-producing Salmonella strains resistant to cefotaxime were identified by broth microdilution method and clavulanic acid inhibition test, including 14 monophasic Salmonella Typhimurium strains and one Salmonella Derby strain. Whole genome sequence analysis showed that nine monophasic S. Typhimurium strains coresistant to colistin and fosfomycin carried the resistance genes bla CTX-M-14, mcr-1 , and fosA3. Conjugational transfer tests demonstrated that the phenotypic and genetic resistance to cephalosporins, colistin, and fosfomycin could cotransfer back and forth between Salmonella and Escherichia coli via an IncHI2/pSH16G4928-like plasmid. Conclusions This study reports the cotransmission of phenotypic and genetic resistance to cephalosporins, colistin, and fosfomycin via an IncHI2/pSH16G4928-like plasmid in Salmonella strains of animal origin, giving an alarm for the prevention of the development and spread of bacterial multidrug resistance. [ABSTRACT FROM AUTHOR]

Staphylococcus aureus is one of the major foodborne pathogens and can cause serious foodborne illness in humans by foods contaminated with S. aureus enterotoxins. In recent years, livestock-associated S. aureus has been a major public health concern for humans and has emerged in various countries globally. China is one of the largest producers of pigs and pork in the world. However, there are few studies on the detailed genotypic and pathogenic characterization of pork-associated S. aureus in China. In this study, the prevalence, antimicrobial resistance, and genotypic characteristics of S. aureus in raw pork in Wuhan, China, were investigated through multilocus sequence typing (MLST), staphylococcal protein A gene (spa) typing, and whole-genome sequencing analysis. A total of 518 S. aureus isolates (16.9%) were isolated from 3067 retail and wholesale pork samples. The prevalence of S. aureus in retail pork (22.7%) was significantly higher than in wholesale pork (15.1%), while the proportion of multidrug-resistant (MDR) isolates in wholesale pork (12.9%) was significantly higher than in retail pork (6.2%). Among the isolates, 10.8% were resistant to three or more antibiotics, with higher rates of resistance to penicillin (88.8%) and erythromycin (58.1%). A total of 28 sequence types (STs) were identified in the 518 isolates, and the predominant type was ST7 (57.5%), followed by ST5 (9.1%). In addition, based on the whole-genome sequences of 39 representative strains, 17 spa types were identified among the isolates, of which t899, t091, and t437 were the most common. Furthermore, 19 staphylococcal enterotoxin (SE) and SE-like (SEl) toxin genes were detected in the isolates, of which selw was the most common type (100%), followed by sei, sem, seo, seu, and selv (46.2%); sey (35.9%); and sea, seg, and sen (33.3%). This study found for the first time that ST7-t091-selw and ST9-t899-SCCmecXII-selw were the predominant genotypes of S. aureus in pork in China, which indicated the spreading of S. aureus with multiple virulence factors, especially with new SE/SEl types in pigs and pork, is a serious new challenge for food safety. Good hygiene and good production practices to prevent interspecies transmission and cross-contamination of S. aureus in the pig–pork chain are of great significance to public health. [ABSTRACT FROM AUTHOR]

Pig is usually the carrier of Salmonella and Staphylococcus aureus, and can transmit the bacteria along the pork production chain to cause severe public health problems. In this study, we investigated the prevalence of Salmonella and S. aureus in fattening pigs in Hubei Province, China. The overall prevalence of Salmonella in rectal swab among 896 samples from 22 farms was 17.30%, and that of S. aureus in nasal swab among 814 samples from 20 farms was 28.26%. Antimicrobial resistance (AMR) analysis showed that 95.33% of the Salmonella strains exhibited resistance to more than three classes of antimicrobial agents tested. The highest resistance proportions were for chloramphenicol (100%), sulfamethoxazole/trimethoprim (SXT) (100%), and tetracycline (TET) (93.46%), while the lowest proportions were for cefotaxime (37.38%), gentamicin (GEN) (34.58%), and ciprofloxacin (24.30%). On the other hand, 98.42% of the S. aureus strains were resistant to more than three classes of antimicrobial agents tested. The most common resistance among the S. aureus strains was against SXT (100.00%), followed by TET (98.43%), erythromycin (91.34%), and clindamycin (91.34%), while the lowest frequent resistances were against GEN (34.65%) and oxacillin (16.54%). The prevalence and AMR of Salmonella and S. aureus exhibited an obvious diversity among different pig farms. Our results provided the epidemiological data for risk analysis of foodborne bacteria and AMR in pig farms. [ABSTRACT FROM AUTHOR]

The antimicrobial resistance of Salmonella strains is rapidly increasing worldwide, which poses significant threats to animal and public health. In this study, a total of 249 porcine Salmonella isolates collected in China during 2008-2015 were examined, including 155 clinical isolates from diseased pigs and 94 nonclinical isolates from healthy pigs. Based on the minimum inhibitory concentration of seven antimicrobial agents, 96.4% of the isolates were resistant to at least one of the tested antibiotics and 81.0% of them showed multidrug resistance. The highest antimicrobial resistance was observed for tetracycline (85.9%), and the lowest was found for cefotaxime (13.3%). The isolates from diseased pigs exhibited significantly higher levels of antimicrobial resistance than those from healthy pigs. Twenty-two isolates from healthy pigs were resistant to ciprofloxacin, which may inhibit the curative effectiveness of fluoroquinolones on bacterial food-borne poisoning and infections in humans caused by contaminated food. Moreover, cefotaxime resistance of the strains isolated from diseased pigs during 2013-2015 was significantly higher compared with the strains isolated during 2008-2010. Further study showed that the correlation between phenotypic and genotypic resistance varied among the isolates from different sources, and in many cases, the presence of resistance genes was not consistent with the resistance to the corresponding antimicrobials. These results are very significant for veterinary practice and public health. [ABSTRACT FROM AUTHOR]