[Studies on the nucleotides sequences of extended-spectrum-beta-lactamases encoding genes of Escherichia coli and Klebsiella pneumoniae and the related molecular evolution].

OBJECTIVE

To identify TEM-type and SHV-type ESBLs encoding genes of ESBLs-producing Klebsiella pneumoniae and Escherichia coli isolated from clinical species in West China Hospital of Sichuan University and study the molecular evolution of the ESBLs.

METHODS

The nucleotide sequences of TEM-type and SHV-type ESBLs encoding genes amplified by PCR were detected by automatic sequencer, and the subtypes of the encoding genes were determined by Blastx searching. The molecular evolution of ESBLs was studied by means of bioinformatics.

RESULTS

In this study, the subtypes of ESBLs were SHV-2 and TEM-19, the distribution of silent mutation in ten bla(SHV-2) was identical, and that of two bla(TEM-19) was the same; the distribution of silent mutation of bla(TEM-19) was the same as that of bla(TEM-1). The distribution of silent mutation of bla(SHV-2) observed here was different from that observed in other countries.

CONCLUSION

SHV-2 was the main ESBLs in this study. The bla(SHV-2) and bla(TEM-19) in this study originated from the same transferable variants respectively. The prevalent SHV-2 in different countries resulted from convergent evolution. It seems possible that the bla(TEM-19) identified by this study might originate directly from the transferable bla(TEM-1) identified in this study.