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Abstract
CRISPR-Cas systems provide adaptive immunity against mobile genetic elements in prokaryotes. This study investigated the occurrence of CRISPR1-cas and CRISPR3-cas in 78 Enterococcus faecalis isolates from endodontic (n=34), oral (n=21), and multidrug-resistant hospital-acquired (n=23) sources, and examined associations with antibiotic resistance and virulence traits. PCR and sequencing were used to detect CRISPR-cas determinants, and phenotypic traits were assessed. CRISPR-cas was significantly more prevalent in endodontic (73%) and oral (71%) strains than in hospital-acquired strains (39%) (P=0.01 and 0.04). Absence of CRISPR-cas correlated with antibiotic resistance (P=0.04) and bacteriocin activity in endodontic strains (P=0.01). Most strains expressing virulence traits carried corresponding gene determinants. These findings suggest that CRISPR-cas may influence genetic exchange and virulence in polymicrobial endodontic environments, with implications for antimicrobial strategies in root canal therapy.