Characterization of Pseudomonas aeruginosa isolated from clinical and environmental samples in Minia, Egypt: prevalence, antibiogram and resistance mechanisms

OBJECTIVES: To assess the prevalence, levels of antimicrobial susceptibility and resistance mechanisms of Pseudomonas. METHODS: A total of 445 clinical isolates and 200 environmental isolates were collected from three hospitals in Minia, Egypt. The MICs of different antibiotics were determined using the agar dilution method. The isolates were tested for beta-lactamase production and for the presence of efflux pumps. RESULTS: Out of the 445 clinical specimens, 107 Pseudomonas strains (24%) and 81 Pseudomonas aeruginosa strains were isolated (18.2%). Out of the 200 environmental specimens, 57 Pseudomonas strains (28.5%) and 39 P. aeruginosa strains were isolated (19.5%). Amikacin was the most active drug against P. aeruginosa followed by meropenem, cefepime and fluoroquinolones. P. aeruginosa was highly resistant to all other antibiotics tested. The environmental isolates of P. aeruginosa exhibited higher antibiotic resistance than clinical isolates. Mechanisms of resistance used by P. aeruginosa included beta-lactamase production and multiple drug resistance efflux pumps. Our results showed that 29 (36%) of the clinical P. aeruginosa isolates and 37 (95%) of the environmental P. aeruginosa isolates were beta-lactamase producers. In addition, P. aeruginosa isolates effectively used an efflux-mediated mechanism of resistance against ciprofloxacin and meropenem, but not gentamicin or cefotaxime. CONCLUSIONS: This study examined the prevalence of P. aeruginosa, and its susceptibility patterns to different antibiotics. The presence of antibiotic-resistant P. aeruginosa isolates could be attributed to beta-lactamase production and the use of multiple drug resistance efflux pumps.