Key words: Clostridium perfringens, Food poisoning

Table 1 Growth of heat-resistant C. perfringens (spore) in chicken soup at different temperatures Hobbs' serological type, ut=untypable Note. Chicken soup was incubated in air up to 72hrs Fig. 1 Effect of temperature on the growth of C. perfringens 'Hama K1' in the chicken soup Fig. 2 Effect of temperature on the growth of C. perfringens 'Hama K1' in the chicken soup

Fig. 3 Effect of ph on the growth of C. per fringens Hama K 1' in the chicken soup at Fig. 5 Effect of salt concentration on the growth of C. perfringens 'Hama K1' in the chicken Fig. 4 Effect of sugar concentration on the growth of C. perfringens 'Hama K 1' in the chicken Fig. 6 Growth of C. perfringens 'HamaK1' in the boiled fish paste (kamaboko) at

Table 2 Degree of spoilage by storage time of boiled fish paste (kamaboko) at 1 Viscous sweat (neto) was found 2 Small colonies of microorganisms were found 3 Many small colonies were grown 4 Many large colonies were grown 5 Surface was covered by bacterial colonies 0 Not spoiled

1) Hobbs, B. C.: Clostridium welchii as a food poisoning organism, J. appl. Bact., 28: 74-82, 1965. 2) Dische, F. E. & Elex, S. D.: Experimental food-poisoning by Clostridium welchii, Lancet, 13: 71-74, 1957. 3) Collee, J. G., Knowlden, J. A. & Hobbs, B. C.: Studies on the growth, sporulation and carriage of Clostridium welchii with special re- to food poisoning strains, J. appl. ference Bact., 24: 326-339, 1961. 4) Barnes, E. M., Despaul, J. E. & Ingram, M.: The behaviour of food poisoning strains of Clostridium welchii in beef. J. appl. Bact., 26: 415-427, 1963. 5) Hall, H. E. & Angelotti, R.: Clostridium perfringens in meat and meat products, Appl. Microbiol., 13: 352-357, 1965. 6) Woodbern, M. & Kim, C. H.: Survival of Clostridium perfringens during baking and hold- of turkey stuffing, Appl. Microbiol., 14: ing 914-920, 1966. 7) Mead, G. C.: Growth and sporulation of Clostridium welchii in breast and leg muscle poultry. J. appl. Bact., 32: 86-95, 1969. 13) Breed, R. S., Murray, F. G. D. & Smith, N. R.: Bergey's manual of determinative bacteriology 7th. Ed., Williams & Wilkins Co., Baltimore, 1957. 14) Mead, G. C.: Combined effect of salt con-

centration and reeiox potential of the medium on the initiation of vegetative growth by Clostridium we/chi. J. appl. Bad., 32: 48: 201-210, 1974. 19) Roberts, TA.: Heat and radiation resistance and activation of spores of Clostridium welchii, Studies on Clostridium perfringens as a causative organism of food poisoning 3. On the growth phase of C. perfringens in foods Shuji NAKATSUGAWA (Shizuoka Prefectural Institute of Public Health, Takajo, Shizuoka, Japan) The present study was undertaken to investigate the growth behavior of C. perfringens (spore) in chicken soup and in boiled fish paste (kamaboko), using six heat-resistant strains isolated from patients or foods with food poisoning. The chicken soup used in this experimentation was composed of 10% minced fowl meat, cooked in water containing 3% sugar and 2% salt, and the boiled fish paste made up of 100 gm of minced fish meat with 6 gm of starch, 4 gm of salt, 3 gm of sugar and 2.4 ml of "mirin" (sweet flavoring sake) added to it. The results of these experiments are summarized as follows: 1. The spore of C. perfringens was capable of growing in chicken soup at temperature range 25-45 Ž. Within the range 30-45 Ž the growth of the organism was fairly more rapid than At 45 Ž, fastest growth was obtaind, an inoculum of 102 spores per ml in soup reached a level as high as 105 viable cell per ml in about 7 hours. No growth occurred at 20 or 2. Sugar contained in the chicken soup was noted to promote the growth of C. perfringens. After reaching the peak of growth, however, the organisms died out rapidly and formed no spores. With the growth of the organism, the soup rapidily became acidified (at ph 4.4 approx.). The higher the temperature of incubation, the faster did the organism die out and the soup show acidification. 3. The growth of C. perfringens was obtained in chicken soup containing 0-5% (w/v) of NaCl within 24 hours at 30 Ž. The growth was not inhibited by NaCl concentrations of 2-3%, but inhibited by 5%. In a soup containing 6% of NaC1 no growth occurred within 96 hours at 30 Ž. The organism was able to grow in soup at ph 5.0 or at ph 9.0, but failed to grow at ph 4.5. 4. The spore of C. perfringens was able to grow in boiled fish paste maintained at 30 Ž, and showing increased viable cell count of 23 from 2.8 ~107 per gram. In contrast, neither outgrowth nor death of C. perfringens spores occurred in boiled fish paste containing 2.5ƒÊg of synthetic preservative "furylfuramide" per gram.