Distribution and resistance mechanism of 16S rRNA methylase in ESBL-producing Klebsiella pneumoniae
Objective To investigate the prevalence and distribution of 16S rRNA methylase gene and research the relationship with drug resistant spectrum.And preliminary explore its role in molecular epidemiology analysis.Methods Collected 69 clinical isolates of non repetitive ESBL-producing Klebsiella pneumoniae in our hospital from Mar to Sep 2010.Detection 16S rRNA methylation enzyme gene by PCR,and analyze ESBL genetype and integron gene of the positive strains.All PCR products were sequenced for determination.Plasmid conjugation test and plasmid elimination method to determine dissemination of 16S rRNA methylase gene.Then we used ERIC-PCR genotyping technology for the establishment of DNA fingerprinting.Results In sixty-nine strains,twenty isolates were rmtB positive (28.9％),two isolates were armA positive,and two strains coproduce rmtB and armA.All positive isolates carried the CTX-M gene,detemined by sequencing,14 strains of CTX-M-14 gene,6 strains of CTX-M-15 gene,14 strains carried TEM1 gene,8 strains carried SHY gene,sequencing showed that 5 strains of SHV-12 gene,3 strains of SHV-11 gene,3 strains carried OXA-10 gene,3 strains carried VBE-1 gene.In addition,the intl gene was found in 12 isolates of 20 rmtB positive strains.All the intl gene positive strains were divided into five kinds gene cassettes,which contained drfA25,drfA1,drfA12,aadA1,aadA2,sat and blaVEB-1 genes.Respectivily,16S rRNA methylase gene positive strains were divided into five genetypes using ERIC-PCR technology.A genetype was the advantage popular clones.Conjugative plasmid and elimination test found that rmtB gene was located in a plasmid in KP5 and KP16 isolates with A genetype,and can disseminate by conjugation.Conclusion A high prevalence of 16S rRNA methylase gene-rmtB was found among clinical ESBL-producing K.pneumoniae isolates in our hospital,which could lead to resistant to almost all aminoglycoside at a high level.Both horizontal gene transfer and clonal spread were responsible for the dissemination of the rmtB gene.In addition,K.pneumoniae co-producing ESBLs,16S rRNA methylation enzymes and class Ⅰ integron existed and were spreading. 
 
Key words: 
Klebsiella pneumoniae; 16S rRNA methylase gene; Intergon; Drug resistance,bacterical