Virulence-associated characteristics of Enterococcus faecalis strains isolated from clinical sources

Abstract

Thirty-two clinical isolates of Enterococcus faecalis were screened for virulence factors. Twenty-four (75%) isolates produced hemolysin on Mueller-Hinton blood agar plates with sheep erythrocytes. However, the cell free heat-stable hemolysin was detected in all isolates (100%) of E. faecalis when grown in BHI-GA (BHI medium supplemented with 1% glucose and 0.03% L-arginine), but not in BHI broth alone. Twenty-four isolates (75%) produced caseinase and 23 (71.9%) lipase, but none of the isolates produced gelatinase. Fifteen (46.9%) culture filtrates caused rounding and membrane alterations with blebbing formation followed by death in HeLa and HEp-2 cells, but not in Vero cells. Thirteen isolates (40.6%) agglutinated rabbit erythrocytes, but did not produce hemagglutination in other bloods, containing or not 1% D-manose. Sixteen (50%) E. faecalis isolates adhered to HeLa cells and thirteen (40.6%) to HEp-2 cells, but all isolates adhered to polypropylene microtiter plates, indicating that clinical E. faecalis possess the ability to form biofilm in vitro. All the isolates were resistant to the bactericidal action of normal serum and did not produce aerobactin. These findings suggest that adherence and consequently biofilm formation on ephitelial host cells are the first steps in the E. faecalis virulence and that hemolysin, lipase, caseinase and other virulence factors act as causative of human epithelial cell damages.

Phenotypic Detection of Virulence Traits and Antibiotic Susceptibility of Endodontic <i>Enterococcus </i><i>f</i><i>aecalis</i> Isolates

“…Hemagglutinating activity was negative in all (100%) E. faecalis isolates with sheep erythrocytes. Our results substantiate the findings of Furumura et al [30].…”

“…Casein hydrolysis was observed in 38 (73%) isolates of E. faecalis. Data does suggest that the gelatin hydrolyzing activity is different from caseinase and also supported previous findings (30). Sedgley et al [33] found that gelatinase gene (gelE) was detected in all endodontic isolates of E. faecalis while expressed gelatinase activity was observed in two thirds of the isolates.…”

“…Previous study [30] indicated that glucose and arginine are essential elements for heat-stable hemolysin production. The production of hemolysin and gelatinase as putative virulence determinants were not always expressed by E. faecalis isolates in association with dental diseases.…”

Evaluating the Anti-Bacterial Activity of Mycelium Extract From Different Wood-Decay-Fungus Species Collected in Southern Vietnam

“…indicates its ability to attack host cell by degrading the membrane proteins and has been considered as one of the basic virulence pathway (Furumura et al, 2006). Our study again confirms the importance of this extracellular type of enzyme in V. paraheamolyticus with its dominance presence (11/17 or 64.7 % tested isolates).…”

Virulence factors and antibiotic susceptibility among verotoxic non O157: H7 Escherichia coli isolates obtained from water and wastewater samples in Cape Town, South Africa.

“…The enzyme is an extracellular zinc endopeptidase that plays a very significant role in bacterial pathogenesis by causing direct or indirect damage to host tissue thus facilitating microbial invasion and survival in the host (Alebouyeh et al, 2005;Furumura et al, 2006). The presence of these enzymes on E. coli isolates is a further confirmation of their potential to cause infections.…”