Virulence profiling, biofilm formation, and antimicrobial resistance pattern of enterococci associated with poultry and livestock feeds

Abstract

Enterococcus spp. represents an important zoonotic opportunistic pathogen. Poultry and livestock feeds could be a source of Enterococci. This study aimed to isolate and identify E. faecalis and E. faecium from poultry and livestock feed samples, determine their antibiotic resistance pattern, and detect their virulence gene, resistance gene, and biofilm formation ability. Among the 84 commerciall mill origin feed samples collected, 82 were PCR screened, of which 19 were positive for E. faecalis and 32 for E. faecium. The antibiogram results revealed that E. faecalis exhibited the highest resistance to Ampicillin in both poultry and livestock feed samples. In poultry feed, this was followed by resistance to Rifampin and Erythromycin, while in livestock feed, additional resistance was observed to Ciprofloxacin and Chloramphenicol. Similarly, E. faecium showed a highresistance to Ampicillin across both sample types. In poultry feed, this was followed by resistance to Erythromycin, Rifampin, and Vancomycin, whereas in livestock feed, it was followed by Erythromycin, Tetracycline, and other antibiotics. Most isolates were positive for multiple virulent genes e.g., agg, pil, fsrB, and fsrC genes. Genotypic analysis revealed the presence of the blaTEM gene in the majority of E. faecalis and E. faecium isolates from both poultry and livestock feed, with slightly higher detection rates in E. faecalis. In the biofilm assay, both E. faecalis and E. faecium demonstrated strong biofilm-forming ability. Current findings reveal that biofilm-forming antibiotic-resistant E. faecalis and E. faecium are present in poultry and livestock feed, which could have implications for public health.