Plasmid-Mediated Quinolone Resistance Genes qnrA, qnrB, qnrC, qnrD, qnrS and aac (6')-Ib in Pseudomonas aeruginosa and Acinetobacter baumannii

Abstract

Background: The emergence and spread of antimicrobial-resistant bacterial isolates is of great concern, especially to commonly used antimicrobials as Quinolones. Aim of the Study: Estimation of the prevalence of quinolone-resistant P. aeruginosa and A. baumannii in various clinical specimens, detection and   characterization of the pattern of plasmid-mediated quinolone resistance genes present. Materials and Methods: Bacterial identification of P. aeruginosa (92) and A. baumannii (69) strains was performed using standard laboratory methods. Antimicrobial susceptibility to other antibiotic was determined by the standard Kirby- Bauer disk diffusion method. All collected quinolones resistant isolates (100) were identified and further subjected to conventional PCR for detection of quinolones resistant genes; namely qnrA, qnrB, qnrC, qnrD, qnrS and aac (6’)-Ib, using specific primers. Sequencing were done for all PMQR positive strains using A BigDye Terminator v3.1 cycle sequencing kit.  Results: PCR revealed 46% of examined quinolone-resistant isolates have one or more of PMQR genes, A. baumannii 28/58 (48.3%) and P. aeruginosa 18/42 (42.9%). The predominant gene detected was aac (6’)-Ib either alone or in combination with other genes. There was significant isolates harboring qnrS gene among P. aeuroginsa which was mainly isolated from outpatients. Sequencing of the PMQR positive strains has confirmed the results of PCR without detection of any new varients or disconcordant strains.    Conclusions: The prevalence rate of quinolone-resistant P. aeruginosa and A. baumannii harboring PMQR genes is high in our hospitals. The acc(6)-1b gene is the PMQR predominant gene coding for quinolone resistance.