Antibiotic-resistant Enterococcus faecium and Enterococcus faecalis in retail shellfish

Food contaminated with antibiotic-resistant enterococci has been implicated as the source of nosocomial infections. Enterococci reside in intestinal tracts of humans and animals as normal flora. In this study, the incidence of antibiotic-resistant enterococci was investigated in shellfish. The data showed the prevalence of E. faecium and E. faecalis was 33% and 8.6% in raw oysters purchased from retail stores. Additionally, in retail cooked shrimp, 3.1% and 14.4% tested positive for E. faecium and E. faecalis, respectively. It was also found that water samples collected from oyster bed areas contained Enterococcus ranging from 2 to 204 enterococci per 100 ml of water. Most of E. faecium isolates from oysters were resistant to trimethoprim/sulfamethoxazole (65.6%) and enrofloxacin (63.3%) while E. faecalis isolates were resistant to enrofloxacin (58.5%). From the shrimp samples, 33.3% of E. faecium and E. faecalis were resistant to enrofloxacin.