Prevalence and molecular characterization of cefotaxime-resistant strains recovered from retail meat samples in Shenzhen, China, during 2014-2017.

In this work, we collected foodborne strains in Shenzhen, China, during 2014-2017 and investigated the genetic profile of all cefotaxime-resistant isolates in the collection. The strains were subjected to antimicrobial susceptibility tests, whole-genome sequencing, bioinformatics analysis, and conjugation studies. A total of 79 cefotaxime-resistant were identified and found to exhibit multidrug resistance. Resistance rate recorded during the study period increased from 1.9% to 9.1%. Typhimurium was the predominant serovar, and CTX-M family genes were dominant among the ESBLs genes detected. Notably, CTX-M-bearing plasmids or transposons often contain other drug resistance genes. Furthermore, a combination of CTX-M-55 and CTX-M-65 genes was detected for the first time in foodborne strains. Our findings reveal the prevalence and molecular characteristics of cefotaxime-resistant foodborne strains in southern China. IMPORTANCE Cefotaxime-resistant strains pose an increasing threat to human health by causing infections with limited treatment options. It is therefore necessary to undertake a surveillance on the prevalence of such strains and investigate the resistance and transmission mechanisms. In this work, various ESBL genes flanked by different IS located in different mobile genetic elements were detectable among cefotaxime-resistant strains. These data show that the high prevalence and genotypic diversity of cefotaxime-resistant foodborne strains in China are possibly attributed to the evolution and transmission of a wide range of multidrug resistance-encoding mobile genetic elements.