Epidemic Plasmid Carrying blaCTX-M-15 in Klebsiella penumoniae in China

ObjectiveTo investigate the local epidemiology of Klebsiella penumoniae carrying blaCTX-M-15 in southern China and to characterize the genetic environment of blaCTX-M-15. MethodsPCR and DNA sequencing were used to detect and characterize the genetic contexts of blaCTX-M-15. The clonal relatedness of isolates carrying blaCTX-M-15 was determined by pulse-field gel electrophoresis. Conjugative plasmids carrying blaCTX-M-15 were obtained by mating and were further subject to restriction analysis and replicon typing. ResultsA 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 blaCTX-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 blaCTX-M-15 in K. pneumoniae. Except blaTEM-1, the resistance genes such as blaSHV, blaDHA-1, blaOXA-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. ConclusionsblaCTX-M-15 was prevalent in K. pneumonia of southern China. The dissemination of blaCTX-M-15 appeared to be due to the horizontal transfer of a 90-kb epidemic plasmid.