Integron-associated resistance genes among multidrug-resistant Pseudomonas aeruginosa isolated from clinical specimens

Aim: To characterize common beta-lactamase genes and the role of integrons in beta-lactam antibiotic resistance among multidrug-resistant (MDR) P. aeruginosa strains isolated from intensive care units in Turkey. Materials and methods: Aft er the examination of 67 P. aeruginosa isolates, 14 were found to be resistant to all of the tested beta-lactams and aminoglycosides. Th ese 14 strains were studied to characterize the beta-lactamases and related integrons. Evaluation of minimum inhibitory concentrations, polymerase chain reaction (PCR) screening, isoelectric focusing, outer membrane isolation and analysis, and cloning and sequencing were performed according to published protocols. Results: PCR screening for common beta-lactamases detected PER-1 and OXA-10 among the selected MDR P. aeruginosa. PCR screening results showed that 2 of the isolates had 5’-3’ class I integrons. Sequence analysis of the integrons revealed the existence of 6’-N-acetyltransferase (aac(6)-Ib) and streptomycin 3’-adenyl transferase (aadA2) cassettes (GenBank accession no. EF368053). Coexistence of PER-1 and OXA-2 and of PER-1 and OXA-10 was demonstrated in 8 and 7 of the isolates, respectively, by PCR. Shotgun cloning and PCR screening with relevant primers revealed the existence of a class I integron-associated blaOXA-2 gene cassette in 2 of the isolates. Strains positive for OXA-2 were also positive for PER-1. Conclusion: Th is study demonstrated the coexistence of PER-1 and OXA-2 in a single host. Coexistence of PER-1 with OXA-2 may increase the risk of the spreading of MDR P. aeruginosa in Turkish hospitals.