Study on CIX-M type ESBLs-producing Escherichia coli and Klebsiella pneumoiae in Guangzhou

Objective To study phylogenies, epidemiology and genetic environment of CTX-M type of ESBLs produced by Escherichia coli and Klebsiella pneumoniae isolated from nine hospitals in Guangzhou. Methods The phylogenies of CTX-M type of ESBLs were analyzed by PCR Genetic environment of CTX-M-15 encoding gene (blaCTX-M-15) were investigated by conjugation test and plasmid analysis. The clonal relationship of strains producing CTX-M-15 was determined by enterobacterial repetitive intergenic consensus PCR (ERIC-PCR). Results A total of 361 ESBLs-producing isolates of Escherichia coli and Klebsiella pneumoniae were collected. 67.3% of ESBLs strains were detected to produce CTX-M-type ESBLs, and the commonest genotypes in Escherichia coli and Klebsiella pneumoniae were CTX-M-14 (35.4% and 28.3%), CTX-M-15(21.5% and 26.1%) EBIC-PCR products of all CTX-M-15-producing strains show 39 strains of Escherichia coli were classified into 27 genotypes while 43 strains of Klebsiella pneumoniae were divided into 30 genotypes. Furthermore, the genotypes of CTX-M-55, CTX-M-19, CTX-M-27, with ceftazidime-hydrelyzing activity, were detected in this study. The great majority of blaCTX-M-15 genes were found to locate on a 65 000 bp-conjugative plasmid, and there was no blaTEM-1, blaOXA-1, blaDSA-1 or aac (6')-Ib-cr gene coexisted on the plasmid, ISEcp1-like insertion sequences, relative to mobilization of blaCTX-M-15 gene, were detected in all blaCTX-M-15 positive strains, and the distances between the end of ISEcp1-like insertion sequences and the start cedon of blaCTX-M-15 were equal, with 48 base pairs. Conclusion CTX-M-14 is still the most common genotype of ESBLs in Guangzhou, but high prevalence of CTX-M-15 ESBLs hydrolyzing ceftazidime already appears in south China. Key words: Escherichia coli;  Klebsiella pneumoniae;  beta-Lactamases;  Escherichia coli proteins;  Phenotype;  Micrebiol sensitivity tests;  Polymerase chain reaction