Antimicrobial resistance patterns and virulence determinants of clinical enterococcus isolates in Pakistan

Background. The current study was designed to determine antibiotic resistance profile,detection of antimicrobial resistance and virulence-related genes among enterococcus species. Materials and methods. Altogether, one hundred fifty enterococcal isolates were collected from various clinical specimens and identified by Polymerase chain reaction (PCR). Antibiotic susceptibility testing and MICs of vancomycin were carried out as per CLSI guidelines. A series of PCR reactions were used to screen vancomycin-resistant genes (vanA, vanB, and vanD) and virulence-related genes (esp, ace, asa1, gelE cylA) among VRE enterococcus species. Results. The isolated enterococcal strains comprised 62.6% E. faecalis, 33.4% E. faecium, and 4% of other species. Overall enterococcus showed a high level of resistance; 94% to erythromycin, followed by ciprofloxacin 82.6%, levofloxacin 70%, and vancomycin 16%. The 57.4% of the isolates were recovered from hospitalized patients and 96% of the enterococcus isolates were multi-drug resistant. The MICs of vancomycin-resistant strains remained in the range of 32 µg/ml to 256 µg/ml for the majority of the isolates. The vancomycin-resistant phenotypes vanA, vanB, and vanD were found in 29.2%, 37.5%, and 33.3% isolates respectively. Regarding virulence determinants the observed percentages were as follows; esp: 16.6%, asa1: 70.8%, gelE: 25%, ace: 33.3%, and cylA: 25%. Conclusion. The majority of the isolates were E. faecalis and multi-drug resistant. The VRE isolates carried antimicrobial resistance and virulence-related genes, and vanA, B, D phenotypes were the most common among VRE isolates.