Dissemination of Class 1, 2, and 3 Integrons Among Multidrug‐Resistant Isolates of Pseudomonas aeruginosa

Pseudomonas aeruginosa is one of the most important opportunistic pathogens, with a central role in nosocomial infections. Bacterial antibiotic resistance caused by mutations in chromosomal genes, acquisition of plasmids, and related to integrons has been reported. This project aimed to investigate Class 1, 2, and 3, and gene cassettes in Class 1 integrons, among 187 clinical isolates of P. aeruginosa from several hospitals in central Iran, with confirmation by standard microbiological assays. Antibiotic resistance testing was performed on 18 antibiotics across different categories using the Kirby-Bauer method according to CLSI standards. Then, the presence of Class 1, 2, and 3 integrons on all isolates and the variable region in the strains containing Class 1 integron was evaluated using a polymerase chain reaction (PCR) assay. Sequenced PCR products by size and analyzed for the determination of gene-cassette arrays. Among isolates, 73 (39.0%) and 14 (7.5%) contained Class 1 and 2 integrons, respectively, and a Class 3 integron was not observed. The amplicons of 800, 1700, and 2200 bp contained gene cassettes, including aadB, blaOXA10-aac(6')-II, and aadB-blaOXA10-aac(6')-Ib. The Antibiotic resistance phenotype of gene-cassette-containing isolates revealed great conformity with the expected phenotype, which depends on the type of resistance genes. Considering the high prevalence of Class 1 and 2 integrons containing gene cassettes for beta-lactamases and aminoglycoside-modifying enzymes among resistant P. aeruginosa isolates, it is necessary to adopt appropriate strategies to control and treat hospital infections to prevent the spread of these genetic elements.