Detection and characterization of class 1 integron-associated gene cassettes from Pseudomonas aeruginosa isolates in southern Taiwan

Abstract

In this study, detection and characterization of class 1 integron-associated gene cassettes from Pseudomonas aeruginosa isolates in southern Taiwan were investigated. The study focused on the association between integron-associated resistance gene cassettes and multidrug resistance in P. aeruginosa isolates. Using polymerase chain reaction amplification, DNA sequencing, and basic local alignment search tool analysis, a total of 22 different types of gene cassette arrays were detected in 162 class 1 integron-positive P. aeruginosa isolates. We first identified 11 different types of new gene cassette arrays within class 1 integron in P. aeruginosa isolates, including aac(6′)-II-catB2-aadA2, aac(6′)-II-aadA2, aac(6′)-II-catB2, aacA4-aadA15, aacC1-orfA-orfB-aadA1, cm1A-aadA1, catB3-bla_OxA-10-aadA15, aacA4-catB8-aadA1, aadB-orfF1-aadA11, dfrB1, and dfrB4a-aacA4-aacA4-aadA1. Of these, aac(6′)-II-catB2-aadA2 was the most frequently found gene cassette. Twenty-one (21/162, 12.9%) strains carrying two different types of gene cassette arrays of catB3-bla_OxA-10-aadA15 and aac(6′)-II-catB2-aadA2 were also simultaneously present in the P. aeruginosa isolates. A novel dfrB4a gene, different from the dfrB4 gene detected in the gene cassette array of dfrB4a-aacA4-aacA4-aadA, was characterized. A metallo-β-lactamaseo gene was also found to be carried on the gene cassette of bla_VIM-3-orf2a-aacA4-aadB-aacA4 inserted in a class 1 integron obtained from meropenem-resistant P. aeruginosa isolates.