Annals of Clinical Microbiology and Antimicrobials (Mar 2018)
Genetic contexts related to the diffusion of plasmid-mediated CTX-M-55 extended-spectrum beta-lactamase isolated from Enterobacteriaceae in China
Abstract
Abstract Background CTX-M-55 extended-spectrum beta-lactamases are being rapidly disseminated and transmitted in clinical practices around the world. The genetic contexts of the transferable plasmid-mediated bla CTX-M-55 gene in Enterobacteriaceae were detected and characterized in this study. Methods Isolates were obtained from the First Affiliated Hospital of Zhengzhou University between September 2015 and March 2016. Based on polymerase chain reaction and BLAST analysis, resistance genes and genetic context of the bla CTX-M-55 gene were investigated. Conjugation experiments and multilocus sequence typing were performed to demonstrate plasmid-mediated bla CTX-M-55 transmission. Results Thirteen bla CTX-M-55-positive isolates of Enterobacteriaceae were obtained. Seven isolates were Escherichia coli, 3 were Klebsiella pneumoniae, 1 was Citrobacter freundii, 1 was Morganella morganii and 1 was Serratia marcescens. The bla CTX-M-55 gene has not previously been identified from C. freundii and M. morganii. Four different bla CTX-M-55 genetic contexts were identified, and all of them harbored ISEcp1 in the region upstream of bla CTX-M-55 (in two cases, ISEcp1 was truncated by IS26, and in one case, it was truncated by IS1294), whereas ORF477 was detected downstream of the bla CTX-M-55 gene from 12 of 13 strains. The novel genetic context of ISEcp1∆-bla CTX-M-55 -∆IS903 was firstly detected the IS903 element which was identified downstream of bla CTX-M-55. A conjugation assay revealed that all bla CTX-M-55 plasmids were quickly and easily transferable to recipient E. coli, which then presented resistance to multiple antibiotics. Conclusions Numerous bla CTX-M-55 -positive strains were isolated in a short period of 7 months. The findings indicate that bla CTX-M-55 was rapidly disseminated. The genetic context and conjugative transfer found in this study demonstrate that there is active transmission of bla CTX-M-55 among strains of Enterobacteriaceae in China, which could give rise to an urgent global public health threat.
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