Epidemic plasmid carrying bla(CTX-M-15) in Klebsiella penumoniae in China.

Objective: To investigate the local epidemiology of Klebsiella penumoniae carrying bla(CTX-M-15) in southern China and to characterize the genetic environment of bla(CTX-M-15).

Methods: PCR and DNA sequencing were used to detect and characterize the genetic contexts of bla(CTX-M-15). The clonal relatedness of isolates carrying bla(CTX-M-15) was determined by pulse-field gel electrophoresis. Conjugative plasmids carrying bla(CTX-M-15) were obtained by mating and were further subject to restriction analysis and replicon typing.

Results: A total of 47CTX-M-15 ESBL-producing isolates of K. pneumoniae were collected from nine hospitals in China from October 2007 to October 2008. Isolates were clustered into various clonal groups. The local spread of bla(CTX-M-15) was mainly mediated by one major conjugative plasmid as determined by S1-PFGE and restriction analysis. A 90-kb plasmid belonging to incompatible group FII was the major carrier of bla(CTX-M-15) in K. pneumoniae. Except bla(TEM-1), the resistance genes such as bla(SHV), bla(DHA-1), bla(OXA-1), qnrB, qnrS, aac(3)-II, and aac(6')-Ib were not found in the plasmid. In the comparing of conjugative gene sequence, it is 100% identical with the plasmid pKF3-94, which was found in K. pneumonia from Zhejiang province of china previously.

Conclusions: bla(CTX-M-15) was prevalent in K. pneumonia of southern China. The dissemination of bla(CTX-M-15) appeared to be due to the horizontal transfer of a 90-kb epidemic plasmid.