Prevalence and molecular characterization of class 1 integrons among clinical isolates of Pseudomonas aeruginosa in Northwest of Iran

Abstract

Integrons are introduced as the most common mechanism for resistance gene dissemination in Pseudomonas aeruginosa. The purpose of the present study was to determine the diversity of the gene cassettes carried with class 1 integrons in clinical isolates of Pseudomonas aeruginosa. One hundred clinical isolates of Pseudomonas aeruginosa from four hospitals in Northwest of Iran were investigated for antimicrobial susceptibility, presence of class 1 integrons and associated resistance gene cassettes. Seventy-one percent of isolates were multidrug resistant (MDR) and colistin was the most effective antibiotic in this study. Sixty-six isolates (66%) were contained class 1 integrons which all of them carried gene cassettes. There was a strong correlation between integron presence and multidrug resistance phenotype (p < 0.05). Amplification of the internal variable regions of class 1 integrons revealed 10 different arrays ranging in size from 0.6 to 3.5 kb. DNA sequencing analysis of class 1 integrons revealed the presence of several gene cassettes associated with resistance to aminoglycosides (aac and aad), beta-lactams (bla (OXA)), chloramphenicol (cmlA and catB), hypothetical gene cassette encoding a hypothetical protein and an open reading frame with unknown function (orfD). The most prevalent gene cassette found within class 1 integrons was aadB (68.18%), followed by aacA4 (48.48%). To the best of our knowledge, some of the gene cassettes arrays such as aac(3)-Ic-aacA5-cmlA5 and aacA5-aadA1-cmlA5 were first identified in this study. Hospital ward was demonstrated as significant risk factors for the acquisition of class 1 integrons harboring isolates in this study (P < 0.05). Most of gene cassette arrays in this study are reported for the first time in Iran. These show the role of integrons in dissemination of resistance genes among clinical isolates of P. aeruginosa.