High prevalence of a class 1 integron-associated aadB gene cassette in Pseudomonas aeruginosa isolates from an Australian cystic fibrosis patient population

Abstract

Pseudomonas aeruginosa is a significant pathogen of patients with cystic fibrosis (CF), and renewed concerns over antibiotic resistance have been raised with reports of potential patient-to-patient transmission of antibiotic resistant clonal strains. A recent study conducted in two CF centres in Brisbane, Australia, identified a dominant clonal P. aeruginosa strain (P2). This P2 clone displayed increased resistance to tobramycin, one of the most commonly used antibiotics in patients with CF. Horizontal gene transfer mechanisms such as plasmids, transposons and integrons containing resistance genes can enhance the spread and development of antibiotic resistance in bacteria. We investigated whether integrons were present in mobile elements present in P. aeruginosa isolates harboured by patients with CF in two Brisbane CF centres, and if these integrons carried associated resistance cassettes.Overall, our results indicate a high occurrence of class 1 integron carriage and class 1 associated aadB gene cassette in P. aeruginosa isolates in Brisbane CF patients. Longitudinal studies are required to determine the true impact of this resistance element, if rates of resistance gene detection change over time, and whether horizontal transfer to other Gram negative bacteria occurs in patients with CF.© 2008 Royal College of Pathologists of Australasia