Molecular basis of quinolone resistance in Enterobacterial isolates

Abstract

Objective: Fluoroquinolones are the commonly prescribed antimicrobial for Gram-negative and Gram-positive microorganisms. The resistance against these antibiotics is of importance in therapy. The current study aimed at determination of aac(6’)-Ib-cr gene within the Enterobacterial isolates and their transmission dynamics. Materials and Methods: Ninety-seven isolates of Enterobacteriaceae collected during May 2013 to October 2013 were screened by the antimicrobial susceptibility test. The plasmids from these isolates were analysed by specific Polymerase chain Reaction (PCR) for qnrA, qnrB, qnrD, qnrC, and aac(6’)-1b-cr and the horizontal dissemination of these plasmid mediated quinolone determinants and aac(6’)-1b-cr genes were determined by transformation. Results: Our analysis showed that 94 out of 97 phenotypically screened positive isolates, 85.57% (n = 83), 84.53% (n=82) were resistant to norfloxacin, ciprofloxacin respectively. Coexisting qnrD genes was identified in 11isolates carrying aac(6’)-Ib-cr gene. The PMQR and aac(6’)-Ib-cr was demonstrated by transforming the plasmid carrying qnrD and aac(6’)-Ib-cr gene into E. coli strain DH5ɑ. PCR assay confirmed that aac(6’)-Ib-cr was present in all the transformants. Conclusion: Our report shows the presence of heterogenous resistance mechanism can lead to worrisome condition at the nosocomial level and community acquired infection. So aac(6’)-Ib-cr containing strains should be promptly detected and referred to clinicians so that the treatment with non-hydrophilic FQs, such as levofloxacin and ofloxacin, or other classes of antibiotics to prevent high level resistance onset and spread. J Microbiol Infect Dis 2016;6(3): 97-102 Aac(6′)-1b-cr, Enterobacteriaceae, plasmid-mediated quinolone resistance, qnrD; qnrC,