A total of 94 patients who had eaten identical meals suffered from diarrhea and abdominal pain in April 2006. Clostridium perfringens was suspected as the causative pathogen based on epidemiological investigation. Bacteriological examination of 60 fecal specimens of the patients using Clostridium welchii (CW) agar with kanamycin (0.2 g/l) and egg yolk for the conventional isolation method identified strains of C. perfringens serotype Hobbs 17 and Hobbs 13 from 49 (81.7%) and 22 (36.7%) of the specimens, respectively. Despite the high isolation rate of these organisms, isolates did not produce C. perfringens enterotoxin. Further examination using CW agar without kanamycin resulted in the isolation of enterotoxin-producing C. pserfringens serotypes TW 1 and TW24 from 31 (51.7%) and 26 (43.3%) fecal specimens, respectively. Both serotypes were isolated from a total of 4 fecal specimens. Although almost all C. perfringens strains are resistant to kanamycin (minimum inhibitory concentration, MIC>256 μg/ml), isolates of serotypes TW 1 and TW24 had MIC for kanamycin of 64-128 μg/ml. Therefore, the number of those that grew onto CW agar without kanamycin were about 1,000∼10,000 times more than onto CW agar with kanamycin.
Nasal samples of humans and animals were examined for the presence of Staphylococcusaureus, and subsequently the incidence of enterotoxigenic and methicillin-resistant S. aureus. Additionally, characteristics of the isolates were studied. The carrier rate of S. aureus was 42.7% (38/89) for humans, 86.4% (57/66) for pigs, 19.8% (20/101) for cows, and 9.5%(4/42) for chickens. By using a commercial SET-RPLA kit, 22 isolates from humans produced staphylococcal enterotoxin (SE) A (n=8), SEB (n=9), and SEC (n=5). S. aureus isolates were subjected to genotyping analysis for detection of se genes (sea to see, seg, seh and sei). The se genes were detected in 25 (65.8%) of 38 human, 34 (59.6%) of 57 pig, and 4 (100%) of 4 chicken isolates. Twenty-five human isolates possessed the sea (n=8), seb (n=4), seb-seg-sei (n=5), sec-sei (n=4), sec-seg-sei (n=1) or seg-sei (n=3) genes. Thirty-four isolates from pigs and 4 isolates from chickens possessed seg-sei genes. MRSA was detected from only 5 food handlers. Phenotypic and genotypic characteristics of 3 MRSA isolates from the 3 food handlers in the same facility were identical except for two phenotypic characteristics. Therefore, the results may suggest that the horizontal transmission of MRSA occurred in the facility.