Detection of a new gene cassette aadA23 in Escherichia coli / 中华传染病杂志

ABSTRACT

Objective Since integrons play an important role in the spread of antibiotic resistance genes in bacteria,the characterization of a new resistance gene cassette in class 1 integron positive strains of E.coli was analyzed. Methods The presence and genetic content of class 1 integron were examined by PCR and sequencing.The sequence was analyzed by using some bioinformatics softwares.Results 5 class 1 integron positive strains were amplified by primers of in-F and in-B which were set for amplifying the region of antibiotics resistance genes.Among the 5 strains,an amplicon of 1009 bp was yielded.Sequencing analysis revealed that amplicon of 1009 bp harbored a 780 bp ORF.Further analysis with bioinformatics software showed that it was 99.6% and 99.5% identical to the known aadA23 and aadA21 cassette,and was just 66.4% identical to the known aadA5 cassette.It was conferring resistant to spectinomycin and streptomycin,and was given a new name aadA23b.Conclusions Multi-drug resistance genes has been proved changeable in E.coli clinical strains.The result not only stressed the need for continuing surveillance of antibiotic resistance in the molecular level,but also the need caring for genetic variation of drug resistance gene cassettes.