Detection of CTX-M-14 extended-spectrum beta-lactamase in Shigella sonnei isolates from China

Shigellosis is an important cause of acute diarrheal disease and multidrug-resistant phenotype has been reported in S. sonnei. In this study, we investigate the resistance and identify extended-spectrum beta-lactamases (ESBLs) gene in 37 S. sonnei isolates by agar dilution procedure and the modified three-dimensional test, respectively. The bla genes of ESBL-producing isolates were detected by polymerase chain reaction (PCR) and sequencing. More than 50% of these strains were resistant to tetracycline, sulfamethoxazole-trimethoprim, ampicillin, ampicillin-sulbactam, or gentamicin. However, they were still susceptible to third generation cephalosporins, fluoroquinolones, and chloramphenicol. A total of 8.1% (3/37) of the isolates with intermediate susceptibility to ceftriaxone and cefotaxime were ESBL-producers, which produced CTX-M-14 ESBLs and TEM-1 beta-lactamases. This is the first report of CTX-M-14 in S. sonnei isolates from China and it is important to closely monitor such strains.