Novel CTX-M β-lactamase genotype distribution and spread into multiple species of Enterobacteriaceae in Changsha, Southern China

Abstract

Objectives: The aim of this study was to undertake a survey of the occurrence of CTX-M and SHV extended-spectrum β-lactamase (ESBL) genotypes in Enterobacteriaceae from Hunan Province, China. Methods: Clinical isolates (425) from three major hospitals in Changsha, Hunan Province, were collected between October 2004 and July 2005, and their antimicrobial susceptibilities of the genotype of blaCTX-M and blaSHV were determined. Random amplified polymorphic DNA was used to characterize the clonality of all of the isolates. Results: The overall rate of ESBL-positive isolates was 33.4% (142/425). The dominant ESBLs were CTX-M types, and were found in 109/142 (76.8%) isolates comprising seven different genera/species, namely Escherichia coli, Klebsiella pneumoniae, Enterobacter cloacae, Enterobacter aerogenes, Citrobacter freundii, Proteus vulgaris and Providencia stuartii. The most common blaCTX-M genotypes were blaCTX-M-14 (47.7%), blaCTX-M-3 (29.4%) and blaCTX-M-15 (17.4%). A novel gene derived from blaCTX-M-15, blaCTX-M-82 (Ala-40→Pro), was identified. Conclusions: The dominant ESBL genotype in Hunan Province was blaCTX-M. The high prevalence (17.4%) of blaCTX-M-15 has not previously been reported from China. Our results identify that an epidemic of blaCTX-M in Changsha, Hunan Province, has evolved with the appearance and spread of blaCTX-M-15 against the dominant genotypes blaCTX-M-14 and blaCTX-M-3. The worldwide dominance of blaCTX-M-15 could be poised to spread to China, displacing the current prevailing genotypes.