Assessment of prevalence, antibiotic resistance, and virulence profiles of biofilm-forming Enterococcus faecalis isolated from raw seafood in Bangladesh

<i>Enterococcus faecalis</i> are often resistant to different classes of antibiotics, harbor virulence determinants, and produce biofilm. The presence of <i>E. faecalis</i> in raw seafood exhibits serious public health significance. This study aimed to identify antibiotic resistance patterns and virulence factors in biofilm-forming <i>E. faecalis</i> strains extracted from seafood in Bangladesh. A total of 150 samples of raw seafood, comprising 50 shrimps, 25 crabs, and 75 fish, were collected and subjected to culturing, biochemical, and PCR assays to detect <i>E. faecalis</i>. The biofilm-forming abilities of the isolates were determined by Congo Red agar (CRA) plate and Crystal Violet Micro-titer Plate (CVMP) tests. Antibiotic resistance profiles were evaluated using the disk diffusion method. Virulence genes of the isolates were detected by PCR assay. The occurrence of <i>E. faecalis</i> was 29.3 % (44/150), which was higher in crabs and fish (36 %) than in shrimps (16 %). In CRA and CVMP tests, biofilm-forming abilities were observed in 88.64 % of the isolates, whereas 11 (25 %) and 28 (63.6 %) were strong- and intermediate-biofilm formers, respectively. All the isolates contained at least two virulence genes, including <i>pil</i> and <i>ace</i> (97.7 %), <i>sprE</i> (95.5 %), <i>gelE</i> (90.9 %), <i>fsrB</i> (79.6 %), <i>agg</i> (70.5 %), <i>fsrA</i> (68.2 %), and <i>fsrC</i> (61.4 %). All the isolates were phenotypically resistant to penicillin, followed by ampicillin and rifampicin (86.4 %), erythromycin (13.7 %), and tetracycline, vancomycin, norfloxacin, and linezolid (2.3 %). Resistant gene <i>bla</i> _TEM was found in 61.4 % of the isolates. Moreover, the study found that <i>E. faecalis</i> strains with strong biofilm-forming capabilities had significantly higher levels of virulence genes and antibiotic resistance (<i>p</i> < 0.05) compared to those with intermediate and/or no biofilm-forming abilities. To the best of our knowledge, this research represents the first instance in Bangladesh of assessing antibiotic resistance and identifying virulence genes in biofilm-forming <i>E. faecalis</i> strains isolated from seafood samples. Our study revealed that seafood is a carrier of antibiotic-resistant, virulent, and biofilm-forming <i>E. faecalis</i>, demonstrating a potential public health threat.