Evaluation of virulence factors in enterococcus species

Abstract

Enterococci have recently become important due to their increased isolation rates in community-based and nosocomial infections and resistance to many antibiotics, including glycopeptides. The aim of this study was to evaluate the antimicrobial susceptible patterns and virulence factors of various clinical specimens; urine (n= 149), blood (n= 38), wound (n= 17), stool (n= 13), and other (n= 12) with a total of 229 enterococci including 138 E.faecalis and 91 E.faecium isolates. Aggregation factor (AF), enterococcus surface protein (esp), cytolysins and gelatinase encoding genes (asa1, esp, cylM, cylBcyl A, cylll, cylls, gelE, respectively) were investigated by molecular methods. Haemolysin production and gelatinase were studied phenotypically. A total of 30 isolates, 29 of E.faecium and one of E.faecalis isolates were resistant to vancomycin. High-level gentamicin and high-level streptomycin resistance in E.faecalis were 40.7% and 63.7% however, they were 47.1% and 55.8% in E.faecalis isolates. All strains were susceptible to linezolid. Ampicillin, penicillin and vancomycin resistance in E.faecium isolates were found to be higher than E.faecalis isolates (p= 0.001, p= 0.008 and p< 0.001). Asa1 (p< 0.001), cylll (p= 0.002) and cylls (p< 0.001) as well as gelatinase activity in isolates of E.faecalis were significantly higher than the isolates of E.faecium (p< 0.001). The most common virulence genes in our study were asa1 gene (45%), cyLs gene (33.2%) and esp gene (32.3%). Ciprofloxacin resistance in cylLL and cyLs gene positive isolates of E.faecalis were significantly higher compared to isolates that do not contain these genes (p= 0.035 and p= 0.047). Likewise, haemolysin producing E.faecium isolates were significantly more resistant to vancomycin compared to isolates that do not produce hemolysin (p< 0.001). When the virulence factors of vancomycin resistant and susceptible isolates were compared, the esp gene level in VRE E.faecium isolates was found to be 24.1%, while no esp gene was found in VRE E.faecalis isolates. The existence of asa1was negative in both VRE E.faecium and VRE E.faecalis isolates. The activity of hemolysin was found 42.3% for E.faecalis and 19.3% for E.faecium. In vancomycin-sensitive enterococcus (VSE) species, esp gene activity was 35.1% for E.faecalis, 29.4% for E.faecium, asa1 gene activity was 60.8% for E.faecalis and 47.1% for E.faecium, hemolysin activity was 52.8% for E.faecalis and 23.5% for E.faecium. In our study, it was found that VSE isolates have more virulence genes than VRE isolates. It should be kept in mind that VRE can causeinfections which are difficult-to-treat especially in hospitalized patients and VSE have significant virulence factors that can cause severe infections.