Frequency of cas genes in the CRISPR/Cas system in ESBL-producing Escherichia coli isolated from urinary tract infection

CRISPR  system (clustered regularly interspaced short palindromic repeats) and Cas portions is a part of the immune system in microorganisms. The cas genes could be involved in reducing antibiotic resistance in bacteria. The aim of the study was to investigate the frequency of cas genes of the CRISPR/Cas system in Extended Spectrum        Beta-Lactamase (ESBL) producing Escherichia coli isolated from urine culture of patients with urinary tract infection.

In this cross-sectional study, 437 positive urine culture samples were collected from Chalus hospitals. Escherichia coli strains were isolated based on standard biochemical tests and Enterobacteriaceae commercial diagnostic kit, as well as antibiotic sensitivity using disc diffusion method (Kerby Baer). Combined disk test was conducted for isolates that were resistant to at least one of the third-generation cephalosporins in the foregoing antibiotic susceptibility test. Molecular identification of cas1,cas2,cas3,cas7 and cas5 genes was performed using the PCR method.

Out of 437 urin culture samples, 106 samples (24.3%) had E.coli infection. The highest antibiotic resistance was associated with ampicillin (99%). Among the resistant isolates, thirty isolates (88.3%) were ESBL producing. cas1 gene had the highest frequency (96.2%) and other cas genes had almost the same frequency.

The results of the present study showed that a significant percentage of E. coli isolates had ESBL phenotype, which may be due to the presence of broad-spectrum beta-lactamase genes in these samples. Besides,  it was shown that there is no relationship between the presence of ESBL phenotype and the distribution of cas genes.