Molecular Epidemiology of the fsr Locus and of Gelatinase Production among Different Subsets of Enterococcus faecalis Isolates

Abstract

We examined 215 Enterococcus faecalis isolates and found that neither the two-component regulatory locus fsr (E. faecalis regulator) nor gelatinase production was more common in disease-associated isolates than in isolates colonizing healthy individuals (ca. 60 to 65%). The majority of gelatinase-negative isolates, including 14 endocarditis isolates (of 80 isolates tested), contained the previously described 23.9-kb deletion and lacked fsrA and fsrB. While these findings indicate that neither fsr nor gelatinase is required for E. faecalis to cause infection, this study did not address whether fsr or gelatinase affects the severity of disease, as it does in animal models.Enterococci are normally commensal flora, but they can cause a wide range of diseases, including urinary tract infections, bloodstream infections, wound infections, and endocarditis (12, 13). Although there are over 20 species of enterococci (8), Enterococcus faecalis isolates cause the majority of infections (22). Despite the increasing number of cases of enterococcal infection and the remarkable ability of these organisms to resist antibiotics, relatively little about their pathogenesis is known compared to what is known about some other grampositive cocci.Despite its role as a possible virulence factor, gelatinase is not produced by all clinical isolates, and a number of studies have attempted to correlate gelatinase activity with disease caused by E. faecalis (3,5,7,17,20,24,28). Nakayama et al. recently reported that a 23.9-kb chromosomal deletion involving the fsr locus was commonly found in urine isolates and was also found in most gelatinase-negative strains (17). In contrast, another study reported that fsr was present in 100% of 12 endocarditis isolates (20). In the present study, we compared clinical isolates of E. faecalis from patients with endocarditis, urinary tract infections, or blood-borne infections to fecal isolates from healthy volunteers with respect to the presence of fsr and gelatinase production.A total of 215 E. faecalis isolates from clinical samples and from feces of healthy, community-based volunteers, collected between 1974 and 2003, were used in this study. The identification of all isolates as E. faecalis was initially done by biochemical tests and was confirmed by using an intragenic portion of the ace gene (18) as a probe for colony hybridization (data not shown). E. faecalis OG1RF (15), E. faecalis OG1SSp (6), E. faecalis V583 (23), and Enterococcus faecium TX0016 (2) are well-studied strains and were used in this study as controls. Brain heart infusion agar (Difco Laboratories, Detroit, Mich.) or brain heart infusion broth was used for growth.

Gelatinase Is Important for Translocation of Enterococcus faecalis across Polarized Human Enterocyte-Like T84 Cells

“…When combined with the translocation results obtained from the previous study (31) and our subsequent determination of their gelatinase activity (17), the capability of translocation of the two groups (GelE ϩ versus GelE Ϫ ) is significantly different, with translocation occurring in a total of 167 out of 185 transwells at 6 h for GelE ϩ strains compared to a total of 7 out of 128 transwells for GelE Ϫ strains (P Ͻ 0.001 by Fisher's exact test). On the other hand, the level of translocation by gelatinase-positive human isolates varied considerably, which cannot be completely explained by the level of gelatinase activity, suggesting that although gelatinase is critical for E. faecalis translocation, other factor(s) are also important in this process.…”

“…A 23.9-kb deletion involving fsrA and fsrB was first described by Nakayama et al in E. faecalis urine isolates obtained from a Japanese hospital (13), and this region was later found by our group, using colony hybridization and PCR, to be absent in 60 E. faecalis isolates (including TX1332 and JH2-2) from different clinical and geographical sources, which account for ca. 28% of the E. faecalis isolates tested by us (17). Neither TX1322 nor JH2-2 showed detectable gelatinase activity or translocation.…”

“…We subsequently examined our results from a survey of 215 E. faecalis isolates (17) and noted that although the assay used was rather crude and the growth conditions were different from those used for translocation, the results suggested a correlation between gelatinase activity and translocation capability of E. faecalis. That is, 6 out of 6 gelatinase-positive isolates translocated across T84 mono-layers in more than 63% of the transwells, 4 out of 7 gelatinasenegative isolates did not show translocation in any of the transwells, 3 out of 7 gelatinase-negative isolates showed translocation in less than 25% of the transwells, and 1 isolate showed weak gelatinase activity and no translocation (unpublished observations).…”

The interactions between esp, fsr, gelE genes and biofilm formation and pfge analysis of clinical Enterococcus faecium strains

“…In clinical enterococcal strains, gelatinase activity is generally associated with virulence factors (Pillai et al, 2002;Roberts et al, 2004). Because of no detection of gelatinase activity or presence of fsr and gelE genes in the tested clinical E. faecium isolates, no significant correlation was found between gelatinase production and fsr, gelE genes and biofilm formation.…”

Vancomycin-Resistant Enterococcus faecalis Endocarditis: Linezolid Failure and Strain Characterization of Virulence Factors

“…One study showed that 100% (12 out of 12) of the E. faecalis endocarditis isolates tested had fsr compared to only 53% (10 out of 19) of the fecal isolates tested (21). In contrast, two subsequent studies did not show an increased prevalence of fsr in E. faecalis endocarditis and bloodstream isolates (11,23). In a rat endocarditis model, an E. faecalis mutant that did not produce gelatinase or serine protease had an endocarditis induction rate that was significantly reduced compared to that of wild-type E. faecalis (28).…”