Association of CRISPR-Cas System with the Antibiotic Resistance and Virulence Genes in Nosocomial Isolates of Enterococcus

This study aimed to investigate the prevalence of the CRISPR-Cas system in nosocomial isolates of and their possible association with antibiotic resistance and virulence genes. Identification and antimicrobial susceptibility of the microorganism were performed by the automatized VITEK 2 Compact system (bioMerieux, France). A total of 100 isolates were collected and identified by VITEK 2 Compact automatic microbial identification drug susceptibility analyzer. The prevalence of various CRISPR-Cas systems, antibiotic resistance genes and virulence genes were investigated by polymerase chain reaction (PCR). The prevalence of CRISPR-Cas systems associated with antibiotic resistance and virulence genes was performed by appropriate statistical tests. A total of 100 isolates of were identified and there were 62/100(62.0%) isolates and 38/100(38.0%) isolates. In total, 46 (46.0%) of 100 isolates had at least one CRISPR-Cas locus. CRISPR elements were more prevalent in isolates. The results of PCR demonstrated that CRISPR1-Cas, orphan CRISPR2, and CRISPR3-Cas were present in 23 (23.0%), 42 (42.0%) and 5 (5.0%) isolates, respectively. Compared with CRISPR-Casnegative isolates, the CRISPR-Cas positive isolates showed significant lower resistance rates against ampicillin, erythromycin, levofloxacin, tetracycline, vancomycin, gentamicin, streptomycin, and rifampicin. Presumably consistent with drug susceptibility, fewer CRISPR loci were identified in , and positive isolates. There was a significant negative correlation between the CRISPR-Cas locus and the enterococcal virulence factors enterococcal surface protein ( ) gene. In conclusion, the results indicated that the absence of the CRISPR-Cas system was negatively associated with some antibiotic resistance in clinical isolates of and . Also, there was a negative correlation with the carriage of antibiotic resistance genes. Furthermore, CRISPR-Cas may prevent some isolates from acquiring certain virulence factors.