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Non-O157 Shiga toxin (stx)–producing Escherichia coli(STEC) is recognized as an important human diarrheal pathogen. Cattle are the principal reservoirs of STEC, although other animals can be carriers. Humans are mainly infected by consuming contaminated drinking water or food. This study aimed to evaluate the virulence potential of isolated bovine non-O157 STEC to humans in Xinjiang. During 2015–2017, 978 rectal swab samples collected from cattle of 5 farms were screened for the presence of Shiga toxin-encoding genes by polymerase chain reaction. Strains identified as STEC were isolated from rectal swab samples, and were characterized for stxsubtype, virulence genes, O serogroup, phylogenetic group, and hemolytic phenotype. Among 125 non-O157 STEC isolates, the prevalence percentages of stx1and stx2were 22 and 21, respectively, and 57% of the isolates carried both Shiga toxins. The stxsubtypes were mainly found in the combination of stx1a/stx2a(57%), stx2a(20%), stx1a(22%), stx1a/stx2a/stx2c(1%), and stx2a/stx2c(1%). The enterohemolysin (ehxA) gene was found in 94% of the isolates. No intimin (eae) was detected. Hemolysis was observed in 33% of the isolates. Two STEC serogroups O145 (17%) and O113 (2%) were found, which were reported to be associated with outbreaks of human disease. Phylotyping assays showed that most strains largely belong to groups A (91%) and B1 (7%). The results of this study can help improve our understanding of the epidemiological aspects of bovine STEC and devise strategies for protection against it.

AbstractExtended-spectrum β-lactamase (ESBL)–producing Escherichia colihave been frequently isolated from food-producing animals and pose a serious threat to human health. This study collected 195 ESBL-producing E. coliisolates from 20 chicken farms and 3 live-bird markets located in Northeast China (Heilongjiang, Liaoning, Jilin) and Jiangsu province from February 2011 to October 2013. ESBL genes, including blaCTX-M, blaTEM, and blaSHV, were detected and characterized, and the susceptibilities of these strains to various antimicrobial agents were determined. One hundred ninety-one of these isolates carried 1 or more blagenes. blaCTX-M, blaTEM-1, and blaSHV-5were identified in 183, 121, and 2 isolates, respectively. The most common blaCTX-Mgenes were blaCTX-M-15(68 strains), blaCTX-M-65(41 strains), blaCTX-M-55(35 strains), blaCTX-M-14(32 strains), followed by blaCTX-M-3, blaCTX-M-13, blaCTX-M-79, and blaCTX-M-101, as well as the chimeric genes blaCTX-M-64, blaCTX-M-123, and blaCTX-M-132. Fifteen strains (7.7%) co-harboring CTX-M-1 group and CTX-M-9 group genes were detected in 195 ESBL-producing strains. Pulsed-field gel electrophoresis of 45 strains showed that these CTX-M-producing isolates belonged to 34 different types. To our knowledge, this is the first study to report the blaSHV-5gene in E. coliisolated from chickens in China. Conjugation experiments demonstrated that the blaCTX-Mand blaTEMgenes could be transferred to E. colistrain J53, while conjugative transfer of the blaSHV-5gene from two isolates was not detectable. blaCTX-Mgenes are carried by many kinds of transferable and untypable plasmids. Our findings demonstrate that the CTX-M enzymes are predominant in both type and quantity.

Staphylococcus aureushas been recognized as an important foodborne pathogen. However, knowledge about the epidemiology and genetic characteristics of S. aureusin the meat production chain from farm to market is limited. The aim of this study was to investigate the genetic characteristics of S. aureusin animal samples isolated from Xinjiang province farms and farmer’ markets, by determining staphylococcal protein A (spa) repeat region and virulence factor typing, and by assessment of antimicrobial resistance. Out of 1324 samples, 128 (9.7%) were positive for S. aureus, 26 (2.0%) of them were identified as methicillin-resistant S. aureus(MRSA) and 88 (6.6%) of them were identified as vancomycin-resistant S. aureus(VRSA). Antimicrobial resistance was determined using the disk diffusion method. S. aureusisolates showed resistance to penicillin G (98.4%), clarithromycin (69.5%), erythromycin (69.5%), vancomycin (68.8%), and tetracycline (67.2%). A total of 80.4% of isolates showed resistance to three or more antimicrobial classes. PCR was used to detect ten virulence genes such as the enterotoxin (sea, seb, and sec), hemolysin (hlaand hlb), clumping factor (clfA), and fibronectin-binding proteins A and B (fnbAand fnbB). Our study showed that isolates harbored two or seven virulence genes. All strains encode hlaand clfA, and half of them encode hlband enterotoxin genes. The spatyping results showed that the 128 isolates were grouped into 32 spatypes. The main spatypes were t127 (22.7%), t2592 (12.5%), t437 (10.9%), and t2616 (10.9%). Notably, isolates of t437 type accounted for 46.2% of the MRSA. Our data indicate that meats in the slaughterhouse and farmers' markets were contaminated with S. aureus. S. aureusvirulence genes and spatypes were diverse, and its antibiotic resistance was serious. The presence of MRSA and VRSA represents potential public health risks and warrants further investigation regarding the driving factors of such resistance and their transmission to humans.