Efflux pump genes and antimicrobial resistance of Pseudomonas aeruginosa strains isolated from lower respiratory tract infections acquired in an intensive care unit

The aim of this study was to determine the antimicrobial resistance rates and the resistance genes associated with efflux pumps of Pseudomonas aeruginosa strains isolated from the patients who acquired lower respiratory tract infection (LRTI) in intensive care unit (ICU). Fifty P. aeruginosa strains isolated from the lower respiratory tract specimens of the patients who acquired LRTIs in ICU were included in this study. P. aeruginosa strains were isolated from tracheal aspirate (27), bronchoalveolar lavage (14) and sputum (9). The susceptibilities of the isolates were investigated by the disk diffusion method. Multiplex PCR assay was carried out for the detection of 13 antibiotic-resistance genes. Antimicrobial resistance rates of the isolates were found high and the highest resistance rate of the isolates studied was determined against to mezlocillin (50%) followed by norfloxacin (48%), ciprofloxacin (46%), meropenem (40%). Fourty-three isolates (86%) were determined to carry one and more resistance genes. NfxB gene was most often determined in the genes that were investigated. The significant relation between the resistance to cefepime, piperacilline/tazobactam and the mexC gene, that between the resistance to mezlocillin, piperacilline/tazobactam, ceftazidime, cefepime and ampC genes, and that between the resistance to ciprofloxacin, norfloxacin and oprJ, oprN and nfxB genes was identified. Resistance caused by genes for carbapenemases, aminoglycoside-modifying enzymes and other mechanisms were not identified in this study. Understanding the prevalence and mechanism of antimicrobial resistance in P. aeruginosa may help to select empirical therapy for nosocomial LRTIs due to P. aeruginosa in our ICU. The Journal of Antibiotics (2012) 65, 9-13; doi: 10.1038/ja.2011.102; published online 16 November 2011