Int.J.Curr.Microbiol.App.Sci (2014) 3(7) 853-857 853 Original Research Article Presence of qnr gene in Environmental and Clinical Pseudomonas aeruginosa isolates in Baghdad Mohammed F. AL-Marjani* Department of Biology College of Science Al- Mustansiriya University, Baghdad Iraq *Corresponding author ABSTRACT Introduction Multidrug - resistant Pseudomonas aeruginosa is a serious challenge for antimicrobial therapy of nosocomial infections, it also has many ways of resistance to antibiotics (1). The broad-spectrum fluoroquinolone antibiotics were introduced in the early 1960 s and are today widely used in human and veterinary medicine (2) . In Gram- negative bacteria, quinolone resistance was for a long time considered to be entirely mediated by mutations in chromosomal genes encoding quinolone targets (that is, DNA gyrase and topoisomerase IV) and/or in regulatory genes of outer-membrane proteins or efflux pumps (3) . Plasmids carrying qnr genes have been found to transmit quinolone resistance. These genes encode pentapeptide repeat proteins that block the action of ciprofloxacin on bacterial DNA gyrase and topoisomerase IV (4). The qnrA1 gene consider the first plasmid- mediated quinolone resistance (PMQR), found in a K. pneumoniae strain isolated in 1994. The qnrB8-like and qnrB9-like alleles were later present in enterobacterial isolates from 1988 (5). The extensive use of ISSN: 2319-7706 Volume 3 Number 7 (2014) pp. 853-857 http://www.ijcmas.com Keywords Pseudomonas aeruginosa, Lomofloxacin, Minimum Inhibitory concentrations (MICs) A total of 78 Pseudomonas aeruginosa isolates (40 environmental and 38 clinical) showing a multidrug resistance phenotype including resistance to fluoroquinolones were included in the current study. Ciprofloxacin was the most active drug against P. aeruginosa followed by Lomofloxacin. The clinical isolates of P. aeruginosa showed higher resistance than Environmental isolates. Minimum Inhibitory concentrations(MICs) for Ciprofloxacin were determined, P .aeruginosa clinical isolates had MICs between (4-256) g/ml, while Environmental isolates had MICs (64) g/ml. By polymerase chain reaction amplification and sequencing, A qnrS gene was present in 21% of clinical Pseudomonas aeruginosa isolates and only one environmental isolate , 13.1 % of clinical isolates with 516 bp amplified product of qnrA isolates. The data of the sequencing of PCR products were revealed ( 99 -100 %) homology with qnr genotype .