Chemotherapy

Research from K. Yamane et al has provided new information about Escherichia coli

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"Resistance to FQs was augmented in an E. coli CSR2 transconjugant, but PCR failed to detect qnr genes, suggesting the presence of novel plasmid-mediated FQ resistance mechanisms. Susceptibility tests, DNA manipulation, and analyses of the gene and its product were performed to characterize the genetic determinant. A novel FQ-resistant gene, qepA, was identified in a plasmid, pHPA, of E. coli C316, and both qepA and rmtB genes were mediated by a probable transposable element flanked by two copies of IS26. Levels of resistance to norfloxacin, ciprofloxacin, and enrofloxacin were significantly elevated in E. coli transformants harboring qepA under AcrB-TolC-deficient conditions. QepA showed considerable similarities to transporters belonging to the 14-transmembrane-segment family of environmental actinomycetes. The effect of carbonyl cyanide m-chlorophenylhydrazone (CCCP) on accumulation of norfloxacin was assayed in a qepA-harboring E. coli transformant. The intracellular accumulation of norfloxacin was decreased in a qepA-expressing E. coli transformant, but this phenomenon was canceled by CCCP. The augmented FQ resistance level acquired by the probable intergeneric transfer of a gene encoding a major facilitator superfamily-type efflux pump from some environmental microbes to E. coli was first identified," wrote K. Yamane and colleagues.

The researchers concluded: "Surveillance of the qepA-harboring clinical isolates should be encouraged to minimize further dissemination of the kind of plasmid-dependent FQ resistance determinants among pathogenic microbes."

Yamane and colleagues published their study in Antimicrobial Agents and Chemotherapy (New plasmid-mediated fluoroquinolone efflux pump, QepA, found in an Eschefichia coli clinical isolate. Antimicrobial Agents and Chemotherapy, 2007;51(9):3354-3360).

For additional information, contact Y. Arakawa, National Institute Infectious Disease, Dept. of Bacterial Pathogenesis & Infection Control, 4-7-1 Gakuen, Tokyo 2080011, Japan.

The publisher's contact information for the journal Antimicrobial Agents and Chemotherapy is: American Society Microbiology, 1752 N St. NW, Washington, DC 20036-2904, USA.

Keywords: Japan, Tokyo, Escherichia coli.

This article was prepared by Science Letter editors from staff and other reports. Copyright 2007, Science Letter via NewsRx.com.