Phenotypic Virulence Characteristics, Virulence Gene Profiles and ERIC-PCR Diversity of Urinary Enterococcus faecalis Isolates from Pregnant Women in the Federal Capital Territory, Nigeria

Abstract Background Enterococcus faecalis is an adaptable opportunistic uropathogen whose adhesion, biofilm formation, extracellular enzyme production and cytolysin-associated traits may promote urinary persistence. The pathogen carries important risks for both mothers and unborn children. However, molecular data describing virulence-gene carriage and strain diversity among urinary isolates from pregnant women in Nigeria remain limited. Methods A cross-sectional study was conducted from October 2025 to January 2026 among pregnant women attending antenatal clinics at selected hospitals across the six Area Councils of the Federal Capital Territory, Nigeria. Clean-catch midstream urine was cultured using standard methods. Twenty-seven presumptive E. faecalis isolates were evaluated for Congo red agar biofilm formation, gelatinase, protease and haemolytic activities. Ten selected isolates were confirmed by PCR targeting the species-specific ddlE gene, quantified for biofilm biomass by crystal-violet microtitre assay, screened for esp, asa1, cylA, hyl and ace , and fingerprinted by ERIC-PCR. Phenotypic associations were assessed using phi coefficients and Fisher’s exact test with Holm adjustment. Spearman correlation assessed the relationship between virulence gene burden and biofilm biomass. Results Among 27 isolates, 17 (63.0%) were Congo red agar biofilm positive, 22 (81.5%) produced gelatinase, 19 (70.4%) produced protease and 14 (51.9%) exhibited beta-haemolysis. Gelatinase and protease were strongly associated (φ = 0.735; Fisher’s exact p = 0.0007; Holm-adjusted p = 0.0042); other pairwise associations were not significant after correction. All ten selected isolates yielded the expected 941-bp ddlE amplicon. By microtitre assay, nine of ten isolates produced biofilm: five strong, three moderate and one weak producer. esp and asa1 were each detected in five isolates, cylA in four, and hyl and ace in one isolate each. Virulence gene burden showed a moderate but non-significant positive correlation with OD 570 (Spearman ρ = 0.547, p = 0.102). ERIC-PCR separated the ten isolates into four clusters and nine fingerprint variants. Conclusion Urinary E. faecalis isolates from pregnant women in the study setting displayed frequent biofilm and extracellular enzyme phenotypes, heterogeneous virulence gene profiles and substantial ERIC-PCR diversity. These findings indicate multiple circulating strain backgrounds with variable pathogenic potential and support larger, prospectively designed molecular surveillance studies.