Characterization of extended-spectrum β-lactamases (ESBLs)-producing Salmonella in retail raw chicken carcasses

Extended-spectrump-lactamases (ESBLs)-producing Salmonella is considered a serious concern to public health worldwide. However, limited information is available on ESBLs-producing Salmonella in retail chicken products in China. The objective of this study was to characterize ESBLs-producing Salmonella isolates from retail chickens in China. A total of 890 Salmonella isolates from retail chicken carcasses collected from 4 provinces were firstly screened for ESBLs-production phenotype via the double-disk synergy test method. A total of 96 (10.8%, n = 890) ESBLs-producing Salmonella were identified and subjected to PFGE analysis, characterization for the presence of ESBLs encoding genes, transposons, carbapenemase and virulence genes. A total of 59 PFGE profiles were detected in these 96 isolates, among which 573% were found to harbor bla(TEM-1), whereas 302%, 24.0%, 18.8% and 7.3% were carrying b/a(OXA-1), b/a(CTXM-15), bla(CTXM-3) and bla(PSE-1) genes, respectively. Moreover, 42 (43.8%) isolates co-carried 2 ESBLs-producing genes, and two (2.1%) isolates co-carried 3 genes. Furthermore, 24 (25.0%) ESBLs-producing isolates carried VIM and 10 (10.4%) carried KPC encoding genes that closely associated with carbapenems resistance. Eighty-eight isolates harbored transposons ranging from 4.2% for Tn903 to 76.0% for Tn21. Out of the 88 Salmonella that harbored transposons, 25%, 22.7%, 23.9%, 10.2% and 1.1% of isolates were found to carry 2, 3, 4, 5 and 6 transposons, respectively. The minimum inhibitory concentration (MIC) values for cephalosporins (ceftriaxone, cefoperazone and cefoxitin) to ESBLs-producing isolates were from 4 to 1024 mu g/mL, for nalidixic acid were from 64 to 512 mu g/mL, for fluoroquinolones (ciprofloxacin, levofloxacin and gatifloxacin) were from 4 to 256 mu g/mL. Twenty-nine virulence genes were detected in the 96 ESBLs-producing isolates with 2.1% harbored spvR (lowest) and 90.6% harbored marTand steB (highest). All isolates carried at least one virulence gene, 833% of the isolates co-carried >= 10, 17.7% 1.0% co-carried >= 15, and 1.0% co-carried 23 virulence genes. Interestingly, 16.7% of the isolates resistant to >12 antibiotics tested and shown to carry >4 transposons and 10 virulence genes. Our findings indicated that ESBLs-producing Salmonella isolated from retail chicken meat in China were highly resistant to antibiotics, frequently harbored transposons, virulence genes, carbapenems hydrolysis enzymes and ESBLs encoding genes. These isolates can pose a significant public health risk. (C) 2017 Elsevier B.V. All rights reserved.