High Prevalence of Extended-Spectrum Beta Lactamases among Salmonella enterica Typhimurium Isolates from Pediatric Patients with Diarrhea in China

We investigated the extended-spectrum beta lactamases among 62 Salmonella enterica Typhimurium isolates recovered from children with diarrhea in a Chinese pediatric hospital. A large proportion of S. enterica Typhimurium isolates were resistant to multiple antimicrobial agents, including ampicillin (90.3%), tetracycline (80.6%), trimethoprim/sulfamethoxazole (74.2%), chloramphenicol (66.1%), cefotaxime (27.4%). Forty-nine (79.0%) of S. enterica Typhimurium isolates were positive for blaTEM-1b and resistant to ampicillin. Thirteen S. enterica Typhimurium isolates (21.0%) were positive for blaCTX-M-1-group and blaCTX-M-9-group, and all isolates harboring blaCTX-M genes were positive for ISEcp1. Two main clones (PFGE type A and D) accounted for nearly 70% of S. enterica Typhimurium isolates, and 7 CTX-M-producing isolates belonged to PFGE type D. Collectively, our data reveal multi-drug resistance and a high prevalence of extended spectrum beta lactamases among S. enterica Typhimurium isolates from children in China. In addition, we report the first identification of blaCTX-M-55 within Salmonella spp. Our data also suggest that clonal spread is responsible for the dissemination of S. enterica Typhimurium isolates.