Antibiotic resistance and assessment of food-borne pathogenic bacteria in frozen foods

One hundred ninety-three frozen food samples collected in Korea various public bazaars from October 2006 to September 2007. Staphylococci were detected in 21.8% of frozen food samples. Staphylococcus aureus was isolated from 17 (8.8%) samples. Other staphylococci isolates were identified as S. warneri (7.8%), S. epidermidis (2.1%), S. xylosus (1.6%), S. eguorum (1%), and S. vitulinus (0.5%). Additionally, the antimicrobial susceptibility of 42 staphylococcal isolates to ten different antimicrobial agents was determined. The staphylococcal isolates demonstrated antimicrobial resistance to mupirocin (31%) oxacillin (14.3%), gentamicin (9.5%), teicoplanin (7.1%) and ciprofloxacin (7.1%). Most of the staphylococcal isolates showed high-level resistance to mupirocin (MIC90, >128 µg/mL). Fortunately, most of the isolates were susceptible to vancomycin. The total bacteria and Escherichia coli count were tested to investigate the microbiological quality of frozen foods. From 193 frozen food samples, 43 (22.3%), 34 (17.6%) and 19 (9.8%) samples were shown to be of unacceptable quality due to total bacteria, coliform and E. coli counts, respectively.