Class 1 integrons in Pseudomonas aeruginosa and Acinetobacter baumannii isolated from clinical isolates.

Resistance to various antimicrobial agents is an increasing problem in Pseudomonas aeruginosa and Acinetobacter baumannii infections. In this study, the roles of integrons were examined in 101 P. aeruginosa isolates and 176 A. baumannii isolates from patients. The frequencies and characteristics of class 1, 2 and 3 integrons were investigated and the horizontal transfer of integrons was assessed. Among these isolates, class 1 integrons with a resistance gene cassette were detected in 69.3% of P. aeruginosa and 31.8% of A. baumannii isolates, but class 2 and 3 integrons were not found. Five novel gene cassette arrays were identified in P. aeruginosa: aacA7-cmlA, aadB-blaOXA,-o-aadA1, aadB-arr-2-cmlA-blaOXA,-o-aadA1, aadB-cmlA-aadA1 and aadB-cmlA-blaOXA-10-aadA15. The integrons found in A. baumannii isolates in this study were previously reported. Horizontal transfer of some class 1 integrons was detected in both P. aeruginosa (2/70) and A. baumannii (5/57). These data confirm the high prevalence of class 1 integrons with a variety of gene cassette combinations among multidrug-resistant P. aeruginosa and A. baumannii clinical isolates.