Food Safety Threats: Molecular Surveillance, Antibiogram and Virulence Profiling of Biofilm Forming <i>Enterococcus faecalis</i> in Bangladeshi Restaurants

Enterococcus faecalis (E. faecalis) is a notable public health bacterium since it can thrive on high-touch surfaces in restaurants. This study aimed to isolate E. faecalis, conduct antibiogram to determine resistance patterns, explore the virulence profile and observe biofilm-forming properties. A total of 90 samples were collected from BAU restaurants, including high-touch surfaces and popular food items. Initial isolation employed culture-based method followed by Gram's staining technique and biochemical tests. Molecular confirmation was achieved via polymerase chain reaction (PCR) targeting the ddl_{E. faecalis} gene specific for E. faecalis. Antibiogram was performed using the Disc Diffusion Test for commonly used antibiotics. Genotypic detection of antibiotic resistance and virulence profile were also explored by PCR. Lastly, the Congo Red (CR) test was done to examine the biofilm-forming isolates. Results indicated a prevalence (30%) of E. faecalis in both food and surface samples, with higher contamination rates in crowded areas. Antibiogram revealed high resistance to Penicillin (100%) and moderate to low resistance towards Tetracycline, Ciprofloxacin, Erythromycin and Chloramphenicol. Shockingly, bla_TEM gene was found in 81.48% of isolates, and 18.51% were detected as multidrug-resistant. We found a very high prevalence of the virulence genes fsrA, fsrB, fsrC, gelE, pil, agg, and ace. Finally, the CR test revealed 33.33% and 44.44% isolates as strong and intermediate biofilm formers respectively. This study reinforces the significance of routine surveillance in combating the spread of antimicrobial resistance through the food chain and the prospective use of E. faecalis as a contamination marker.