New subtype of gyrA gene in multi-drug resistant strains of Escherichia coli isolated from urine / 中华微生物学和免疫学杂志

ABSTRACT

Objective To investigate the distribution and variety of quinolone-resistance genes in multi-drug resistant strains of Escherichia coli (E. coli) isolated from urine. Methods From October 2008 to March 2009, 28 strains of multi-drug resistant E. coli isolated from urine were collected from Ningbo No. 1 Hospital, China. One kind of chromosome-mediated quinolone-resistance gene(gyrA) and 5 kinds of plas-mid-mediated quinolone-resistance genes[qnrA, qnrB, qnrS, aac(6')- Ⅰb-Cr, qepA]were analyzed by PCR and verificated by DNA sequencing. Results In 28 strains ofE. coli, only 1 strain was detected to harbor aac(6')-Ⅰb-Or (confirmed by DNA sequencing and genomic comparison with sequence registered in NC-BI), but qnrA, qnrB, qnrS, qepA could not be detected. Furthermore, all 28 strains(100.0%) contained mutations at 83rd coden in gyrA TCG→TTG(mutations at 83rd amino acid S83L). However, 22 strains (78.6%) contained mutation at 87th ceden in gyrA. Among them, 21 strains(75.0% ) contained muta-tions GAC→AAC(mutations at 87th amino acid D87N) ; while gyrA gene of NB005 (3.6%) contained mutations GAC→TAC(mutations at 87th amino acid D87Y), which was a new subtype(GenBank Acces-sion No. GQ286174). And other 6 strains contained no mutation at 87th coden. Conclusion All isolates of E. coli contained mutations in gyrA(100.0%), which play a key role in resistance to quinolones antimi-crobial agents, but positive rate of other resistance genes is low.