Distribution of cylA, esp, asa1, hyl and gelE virulence genes among clinical isolates of Enterococcus faecium and Entrococcus faecalis

Improved detection of esp, hyl, asa1, gelE, cylA virulence genes among clinical isolates of Enterococci

Objective

Virulence factors (VFs) among the clinical strains of enterococci play a vital role in pathogenesis. This study was aimed to screen for cylA, asa1, gelE, esp and hyl among Enterococcus faecalis (n = 89) and E. faecium (n = 51) by multiplex PCR. The previously reported multiplex PCR was modified to 2 duplex (asa1 and gelE, cylA and esp) PCRs and 1 simplex (hyl) PCR. The idea of the modification of the multiplex PCR proposed here emerged in the course of the research study when majority of the isolates which phenotypically exhibited virulence traits were found to be negative for the respective gene.

Results

cylA, gelE and asa1 were significantly predominant in E. faecalis (59.55%, 85.39%, 86.51%) than E. faecium (1.96%, 60.78%, 9.80%) (p < 0.0001, p = 0.001967, p < 0.0001). hyl was detected in E. faecium (5.9%) only. The number of VFs detected in each isolate was recorded as the VF score. E. faecalis isolates had a VF score pattern of score 4 (34.83%), score 3 (26.96%), score 2 (28.08%) and score 1 (8.98%) while E. faecium had score 4 (1.96%), score 3 (7.84%), score 2 (25.49%) and score 1 (41.18%). This modification of the PCR protocol could resolve the problem of decreased detection of virulence determinants in enterococci.

Prevalence of virulence and resistance to antibiotics in pathogenic enterococci isolated from mastitic cows

The prevalence of enterococci was examined in 280 milk samples collected from dairy cattle diagnosed with mastitis in three provinces of western China. Sixty strains of enterococci were isolated, and the species were determined based on their biochemical characters and 16S rRNA sequences. Resistance to seven antibiotic agents, frequency of seven virulence genes and pathogenicity in Kunming mice were tested to evaluate biological risks. The correlation between the number of virulence genes and pathogenicity in Kunming mice was also evaluated. The 60 isolates were allocated to Enterococcus hirae (68.3%), E. faecium (25.0%), E. mundtii (3.3%) and E. durans (3.3%). A total of 83.3% of the isolates were resistant to penicillin, whereas 15.0% were resistant to ampicillin, 15.0% to vancomycin, 6.7% to tetracycline and 25.0% to ciprofloxacin. Moreover, isolates exhibited 50.0% and 21.7% resistance to high levels of gentamycin and streptomycin, respectively. The gene asa1 was detected in all enterococcal isolates, whereas 66.7% of strains harbored three or more virulence factors and 56.7% were asa1-ccf-gelE-positive. In pathogenicity tests, isolates harboring numerous virulence factors did not show greater invasiveness than isolates harboring fewer virulence traits against Kunming mice. In conclusion, the number of virulence factors does not appear to predict the risk of enterococcal infection. Isolates were commonly resistant to penicillin and sporadically to ampicillin and vancomycin. These results suggest that the use of gentamycin, streptomycin and ciprofloxacin against enterococci should be avoided in mastitic cows. Additionally, the results demonstrate that the majority of isolates are sensitive to tetracycline.

Incidence of virulence determinants in clinical Enterococcus faecalis and Enterococcus faecium isolates collected in Bulgaria

Objectives

To evaluate the prevalence of some virulence genes among 510 clinical Enterococcus spp. isolates and to assess the association of those genes with the species, infection site, and patient group (inpatients/outpatients).

Methods

Adhesins genes (aggregation substances agg and asa1 of Enterococcus faecalis and Enterococcus faecium, respectively), enterococcal surface protein (esp), endocarditis-specific antigen A (efaA), collagen-binding proteins (ace/acm)); invasins (hyaluronidase (hyl) and gelatinase (gelE)); cytotoxines (activation of cytolysin (cylA) in E. faecalis); and modulators of the host immunity and inflammation (enhanced expression pheromone (eep) in E. faecalis) were detected by polymerase chain reaction.

Results

The overall prevalence was: esp – 44.3%, agg/asa1 – 38.4%, ace/acm – 64.3%, efaA – 85.9%, eep – 69.4%, gelE – 64.3%, hyl – 25.1%, and cylA – 47.1%. E. faecalis isolates had significantly higher frequency of adhesin genes (esp and agg/asa1) and gelatinase in comparison to E. faecium. Multiple virulence genes in E. faecalis were significantly more prevalent than in E. faecium isolates. Domination of E. faecium with or without only one gene compared to the isolates of E. faecalis were found. Enterococcus spp. isolates obtained from outpatients compared to inpatients isolates had significantly higher frequency of agg/asa1, eep, gelE and cylA. Some adhesins genes (esp, agg/asa1 and efaA) had higher prevalence among the non-invasive Enterococcus spp. isolates compared to those causing invasive bacteremia, while ace/acm revealed higher dissemination in isolates causing invasive infections compared to non-invasive isolates.

Conclusion

Most E. faecalis attaches to abiotic surfaces in hospital environment, which correlates with higher prevalence of gene encoding for virulence factors involved in biofilm formation, such as enterococcal surface protein, aggregation substance, and gelatinase. The intestinal tract is an important reservoir for opportunistic enterococcal pathogens and allows them to access infectious sites through different virulence factors, demonstrated in outpatient isolates in this study.