Virulence factors, antimicrobial resistance and biofilm formation in Enterococcus spp. isolated from retail shrimps

• Enterococcus were present in 80% of ready-to-eat, 55% of raw, 40% of cooked shrimps.
• Resistance to tetracycline, tigecycline and fosfomycin was common.
• 45,7% of Enterococcus isolates were multidrug resistant.
• All of the isolates, carried between 5 and 9 tested virulence genes.
• Enterococcus isolates showed a moderate or weak ability to produce biofilm.

A total of 60 samples from retail raw, cooked and ready-to-eat shrimps were collected and the prevalence of Enterococcus spp, their virulence factors, antibiotic resistance and biofilm-forming ability was determined. Most of the strains were isolated from ready-to-eat shrimps (16/20; 80%) followed by raw shrimps (11/20; 55%) and cooked shrimps (8/20; 40%). Among the 35 isolates, Enterococcus faecalis (62.9%) and Enterococcus faecium (28.6%) were the dominant species. More than half of all investigated isolates (65.7%) were resistant to at least one class of antibiotic, and 16 (45.7%) of the strains were classified as multidrug resistant. A high percentage of isolates were resistant to tetracycline (48.6%), followed by tigecycline and fosfomycin (45.7%). All of the enterococci isolates, carried between 5 and 9 tested virulence genes. The presence of esp (100%), gelE (88.6%), efaA (77.1%) genes and sex pheromones cpd (100%) cob (94.3%), ccf (94.3%) were found most frequently in all of the tested enterococci species. Shrimp strains showed a moderate or weak ability to produce biofilm. Our data indicate that shrimps can be considered a reservoir of antibiotic resistant, virulence strains from the genus Enterococcus.