AUTHOR=Zhang Chuan-Zhen , Ding Xiao-Min , Lin Xiao-Ling , Sun Ruan-Yang , Lu Yue-Wei , Cai Run-Mao , Webber Mark A. , Ding Huan-Zhong , Jiang Hong-Xia 

TITLE=The Emergence of Chromosomally Located blaCTX-M-55 in Salmonella From Foodborne Animals in China

JOURNAL=Frontiers in Microbiology

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2019.01268

DOI=10.3389/fmicb.2019.01268

ISSN=1664-302X

ABSTRACT=<p>The emergence and increase in prevalence of resistance to cephalosporins amongst isolates of <italic>Salmonella</italic> from food animals imposes a public health threat. The aim of the present study was to investigate the prevalence and characteristics of CTX-M-producing <italic>Salmonella</italic> isolates from raw meat and food animals. 27 of 152 (17.76%) <italic>Salmonella</italic> isolates were ESBL-positive including 21/70 (30%) from food animals and 6/82 (7.32%) from raw meat. CTX-M-55 was the most prevalent ESBL type observed (12/27, 44.44%). 7 of 12 CTX-M-55-positive <italic>Salmonella</italic> isolates were <italic>Salmonella</italic> Indiana, 2 were <italic>Salmonella</italic> Typhimurium, 2 were <italic>Salmonella</italic> Chester, and the remaining isolate was not typeable. Eight CTX-M-55-positive <italic>Salmonella</italic> isolates were highly resistant to fluoroquinolones (MIC<sub>CIP</sub> = 64 ug/mL) and co-harbored <italic>aac(6’)-Ib-cr</italic> and <italic>oqxAB</italic>. Most of the CTX-M-55 positive isolates (11/12) carried <italic>bla</italic><sub>CTX-M-55</sub> genes on the chromosome, with the remaining isolate carrying this gene on a transferable 280 kb IncHI2 plasmid. A chromosomal <italic>bla</italic><sub>CTX-M-55</sub> gene from one isolate transferred onto a 250 kb IncHI2 plasmid which was subsequently conjugated into recipient strain J53. PFGE and MLST profiles showed a wide range of strain types were carrying <italic>bla</italic><sub>CTX-M-55</sub>. Our study demonstrates the emergence and prevalence of foodborne <italic>Salmonella</italic> harboring a chromosomally located <italic>bla</italic><sub>CTX-M-55</sub> in China. The co-existence of PMQR genes with <italic>bla</italic><sub>CTX-M-55</sub> in <italic>Salmonella</italic> isolates suggests co-selection and dissemination of resistance to both fluoroquinolones and cephalosporins in <italic>Salmonella</italic> via the food chain in China represents a public health concern.</p>