Potential Co-prevalence of Plasmid-Mediated Quinolone Resistance Determinant qepA and 16S rRNA Methylase rmtB among E.coli Clinical Isolates from Alexandria- Egypt.

BACKGROUND Fluoroquinolone-resistant Gram-negative pathogens have been increasingly reported from most regions of the world over the last decade. A new plasmid-mediated fluoroquinolone efflux pump gene (qepA) is known to be associated with the 16S rRNA methylase gene (rmtB) that confers resistance to aminoglycosides. AIM To investigate the potential co-prevalence of qepA and rmtB genes in Escherichia coli (E. coli) clinical isolates collected from Egyptian medical facilities. MATERIAL AND METHODS A total of 225 non-duplicate E. coli isolates were collected between 2008 and 2009 from two hospitals in Alexandria. Isolates were initially tested for their antibiotic susceptibility by disc diffusion method. Isolates exhibited quinolone and aminoglycosides co-resistance profile were screened for the presence of qepA and rmtB genes. The effect of efflux pump inhibitor, phenylarginine-beta-naphthylamide (PAβN) on the minimum inhibitory concentration (MIC) of ciprofloxacin, levofloxacin and gentamicin against these strains was tested and log activity index was calculated. Using checkerboard titration method, the combinations of gentamicin with ciprofloxacin against the strains harboring qepA and rmtB genes were tested and the fractional inhibitory concentrations (FIC) were calculated. RESULTS Forty-five E. coli isolates exhibited quinolone and aminoglycosides co-resistance profile. Of them, two E. coli isolates were positive for qepA, and three harbored rmtB genes. No association between both genes was detected. The calculated log activity index revealed a reduction in MIC of the fluoroquinolones with PAβN but not of gentamicin. FIC calculated here for gentamicin/ciprofloxacin combinations reflected either antagonism or indifference against the strains harboring qepA and rmtB genes. CONCLUSION AND RECOMMENDATIONS qepA as well as rmtB genes-carrying E. coli strains could become a greater nosocomial infection problem with appropriate foci of selective pressure. Therefore, public health support for active surveillance for plasmid mediated fluoroquinolones, aminoglycosides resistance determinants among clinical E. coli isolates should be encouraged. In addition, the effect of efflux pumps needs to be considered in the design of future antibiotics as their synergistic role may pave the way to novel combination therapies that could be used against these strains.