Novel CTX-M {beta}-lactamase genotype distribution and spread into multiple species of Enterobacteriaceae in Changsha, Southern China.

OBJECTIVES: The aim of this study was to undertake a survey of the occurrence of CTX-M and SHV extended-spectrum beta-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 bla(CTX-M) and bla(SHV) 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 bla(CTX-M) genotypes were bla(CTX-M-14) (47.7%), bla(CTX-M-3) (29.4%) and bla(CTX-M-15) (17.4%). A novel gene derived from bla(CTX-M-15), bla(CTX-M-82) (Ala-40-->Pro), was identified.

CONCLUSIONS: The dominant ESBL genotype in Hunan Province was bla(CTX-M). The high prevalence (17.4%) of bla(CTX-M-15) has not previously been reported from China. Our results identify that an epidemic of bla(CTX-M) in Changsha, Hunan Province, has evolved with the appearance and spread of bla(CTX-M-15) against the dominant genotypes bla(CTX-M-14) and bla(CTX-M-3.) The worldwide dominance of bla(CTX-M-15) could be poised to spread to China, displacing the current prevailing genotypes.