Novel PCR detection of CRISPR/Cas systems in Pseudomonas aeruginosa and its correlation with antibiotic resistance.

CRISPR (clustered regularly interspaced short palindromic repeats)-Cas (CRISPR-associated proteins) systems are considered as acquired immune mechanisms in Gram-positive and Gram-negative bacteria and also in archaea. They provide resistance/immunity to attacking bacteriophages or mobile genetic elements as integrative conjugative elements (ICE) as well as plasmid transformation. As an opportunistic pathogen, Pseudomonas aeruginosa has been held responsible for serious infections especially in hospitalized and immunocompromised patients. Three subtypes of type I CRISPR system (I-C, I-E, & I-F1) have been detected in P. aeruginosa genomes. In this work, P. aeruginosa isolates were collected from different clinical sources, and the three CRISPR/Cas subtypes (I-C, I-E, & I-F1) were detected via singleplex and multiplex PCR techniques using novel universal primers that were designed specifically in this study. CRISPR subtypes I-C, I-E, and I-F1 were detected in 10, 9, and 13 isolates, respectively. Furthermore, antimicrobial susceptibility of CRISPR/Cas-positive and negative isolates to different antibiotics and the capacity of biofilm formation were detected using disc diffusion method and tissue culture plate method, respectively. There was a significant correlation between the presence/absence of CRISPR/Cas system and both antimicrobial susceptibility to some antibiotics and biofilm-forming capacity among P. aeruginosa clinical isolates. KEY POINTS: • A novel multiplex-PCR for detection of CRISPR/Cas-positive strains of P. aeruginosa. • Understand the correlation between CRISPR/Cas systems and other characters of P. aeruginosa. • Correlation between antimicrobial susceptibility and CRISPR systems in P. aeruginosa.