Analysis on drug-resistant gene of CTX-M extended-spectrum β-lactamase-producing Escherichia coli

Objective To study the detection rates and genotype distribution of CTX-M extended spectrum β-lactamases(ESBLs)in ESBLs-producing Escherichia coli(E.coli)clinical isolates from a hospital.Methods On hundred and ninety-seven ESBLs-producing E.coli isolated between January and December in 2005 were performed confirmation test and conjugation test to determine the horizontal transmission of ESBLs,and the ESBLs genes were detected by polymerase chain reaction(PCR),the genotypes of β-lactamases were confirmed by sequencing of the PCR products.Results Among 197 strains,104(52.79%)E.coli isolates produced ESBLs,91 of 104 ESBLs-producing E.coli were tested by conjugation,64(70.33%)transconjugants were acquired.All transconjugants were confirmed to produce ESBLs.98 strains(94.23%)carried the genes of CTX-M,38 strains(36.54%)of which were the blaCTX-M-1 group,and 69 strains(66.35%)were the blaCTX-M-9 group.51 transconjugants(79.69%)carried the genes of CTX-M,18 strains(28.13%)of which were the blaCTX-M-1 group,and 35 strains(54.69%)were the blaCTX-M-9 group.Five CTX-M genotypes were confirmed by sequencing of the PCR products.They were CTX-M-22,CTX-M-28,CTX-M-15,CTX-M-14,CTX-M-27,and CTX-M-14 was the main genotype.Conclusion The prevalence of ESBLs in this hospital is high and the horizontal transmission of ESBLs is serious among the clinical E.coli isolates.The CTX-M-14 is the dominant epidemic type in this hospital,and CTX-M-22,CTX-M-28,CTX-M-15 and CTX-M-27 also exist.