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.
