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Characterization of extended-spectrum beta-lactamases-producing Salmonella strains isolated from retail foods in Shaanxi and Henan Province, China

Yang, Baowei, Wang, Qianning, Cui, Shenghui, Wang, Yin, Shi, Chao, Xia, Xiaodong, Xi, Meili, Wang, Xin, Shi, Xianming, Wang, Dapeng, Zhang, Zengfeng, Meng, Jianghong
Food microbiology 2014 v.42 pp. 14-18
Escherichia coli, Salmonella enterica, antibiotic resistance, beta-lactamase, ceftriaxone, foods, genes, genetic variation, nucleotide sequences, plasmids, pulsed-field gel electrophoresis, sequence analysis, serotypes, China, Indiana
Extended-spectrum beta-lactamases (ESBL)-producing Salmonella enterica have been reported worldwide. However, research on foodborne ESBL-producing Salmonella has been rarely conducted. One hundred and thirty eight ceftriaxone or/and cefoperazone-resistant Salmonella strains recovered from retail foods in Shaanxi and Henan Province, China, were screened for ESBL. The ESBL-producing strains were further characterized for antimicrobial resistance, pulse field gel electrophoresis (PFGE) profiles, and the presence of blaTEM, blaSHV, blaOXA, blaCTX-M, and blaPSE. The transferability of ESBL encoding genes to a susceptible Escherichia coli strain was also investigated. Thirty (21.7%) isolates were identified as ESBL positive and belonged to S. enterica serovars Indiana, Shubra, Typhimurium, and Enteritidis. S. Indiana and S. Shubra isolates were firstly identified in ESBL-producing strains. Great genetic diversity was seen among these ESBL-producing strains. Nucleotide sequence analysis revealed that blaTEM-1B was the only ESBL-encoding gene among the genes tested and was detected in 26 of 30 strains and was carried in the conjugative plasmids. The blaTEM-1B gene was transferable through conjugation at rates ranging from 4.71 × 10−7 to 7.55 × 10−6 transconjugant per recipient cell. This study provides the evidence of foodborne ESBL-producing Salmonella, and the transferability of plasmid harboring ESBL-encoding genes could possibly contribute to the dissemination of ESBL.