Phenotype–genotype correlations and distribution of key virulence factors in enterococcus faecalis isolated from patients with urinary tract infections

Abstract

Background and Objective: Enterococcus faecalis can cause different nosocomial infec-tions, especially urinary tract infection (UTI). Pathogenicity of E. faecalis is driven by various virulence factors; however, no specific genetic pattern is restricted to a particular type of infection. The current study aimed to investigate the correlation between different virulence factors in E. faecalis clinical isolates causing UTIs. Methods: We phenotypically analyzed 60 urinary isolates, identified as E. faecalis, for biofilm formation, gelatinase, protease and hemolytic activities by Crystal Violet assay, gelatin hydrolysis, casein hydrolysis and blood agar hemolysis assays, respectively. Additionally, we detected different genes associated with species identification, virulence phenotypes, adherence and quorum sensing by the polymerase chain reaction (PCR). The detected genes included D-alanine-D-alanine ligase (ddl), cytolysin (cyl), gelatinase (gelE), serine protease (sprE), faecal streptococci regulator locus genes (fsrA, fsrB, fsrC), pili (pil), adhesin to collagen of E. faecalis (ace) and aggregation substance (agg). Results: All isolates formed biofilms, mostly with strong to moderate ability. Although gelE was detected in 87% of the isolates, only 22% of the isolates had gelatinase activity. Similar phenotype–genotype incongruities were observed with hemolysis and casein hydrolysis activities, as the isolates that expressed these two phenotypes were fewer than those carrying the genes encoding them. Conclusion: A clear variability in virulence gene distribution among the isolates was observed, and no particular pattern was associated with UTI. Whereas all isolates carried at least ace and pil, whose products are involved in adherence, which is a virulence phenotype that is required for urinary colonization, six isolates carried the entire set of investigated genes. Statistical analysis of the results suggests cyl as a biomarker for hemo-lytic activity, fsrB as a diagnostic biomarker for the gelatinase activity, and gelE-sprE as predictors for biofilm formation strength in E. faecalis.