Prevalence and molecular analysis of antibiotic resistance of Pseudomonas aeruginosa isolated from clinical and environmental specimens in Basra, Iraq

The steady increase in the spread of multidrug-resistant Pseudomonas aeruginosa (MDR) has become a major threat to the global health systems, including Iraq. This study aimed to investigate the prevalence and the molecular basis of antibiotic resistance in Pseudomonas aeruginosa isolated from clinical and environmental samples.

Pseudomonas aeruginosa strains were identified by standard microbiological procedures followed by PCR confirmation. Antibiotic susceptibility testing, for 16 antimicrobials, was conducted according to the Clinical and Laboratory Standard Institute (CLSI) standardized by disk diffusion and VITEK 2 methods. Detection of beta-lactamases (ESBLs, AmpC and carbapenemase) activities and related encoding genes was performed by using phenotypic methods and PCR technique respectively.

A total of 81 clinical specimens and 14 environmental samples were positive for P. aeruginosa. Antimicrobial susceptibility test showed high rates of resistance to antipseudomonal cephalosporines (74.74 to 98.95%), aztreonam (82.11%), antipseudomonal carbapenems (68.4%), piperacillin/tazobactam (69.5%) ciprofloxacin (71.6%), and aminoglycosides (69%), with emergence of resistance to colistin (7.4%) among tested P. aeruginosa. Among the tested isolates, 69 (72.63%) strains were MDR, of which 63 (91.3%) strains were extremely drug resistance (XDR). Most of the isolated strains harbored one or more of ESBL genes (blaSHV-2a, blaCTX-M-28, blaVEB-2, blaOXA-677, blaPER) with predominant blaOXA-677, but none of the MBLs (GIM, SIM, SPM, IMP) and AmpC (FOX) genes were detected.

The results highlighted a high prevalence rate of MDR and XDR and emergence of colistin resistance P. aeruginosa at Basra hospitals, Iraq.