Study on blaCTX-M-9 group extended-spectrum β-lactamase in Escherichia coli

OBJECTIVE To study the detection rates and genotype distribution of blaCTX-M-9 group extended spectrum β-lactamases(ESBLs) in Escherichia coli(E.coli) clinical isolates.METHODS One hundred and forty-five E.coli isolated between 2005 and 2006 were collected,Double-disk synergy test was used to detect ESBLs,and the blaCTX-M-9 group ESBLs genes were detected by polymerase chain reaction(PCR).The genotypes of β-lactamases and mutation sites were confirmed by sequencing of the PCR products.RESULTS Among 145 E.coli strains,114 strains(78.6%) carried the genes of blaCTX-M-9 group,60 strains(82.2%) of 73 strains in 2005 and 54 strains(75.0%) of 72 strains in 2006.All positive strains were the CTX-M-14-type.25 strains of E.colI in CTX-M-14 gene find five point mutations,lead to 80,158,242,275 bits amino acid changing.CONCLUSION The prevalence of blaCTX-M-9 group 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,including the change of the corresponding amino acid sequence.