Incidence of Clostridium perfringens in Fishes (II)

On the Detection Rate of Clostridium perfringens Type A and Heat-Resistance of Isolated Strains

Abstract

An attempt was made to detect Clostridium perfringens in raw sea-foods from June to September when food poisoning occurs most commonly. The heated and unheated specimens of the body surface and of the alimentary canal of the sea-foods (193 samples) shown in Table 1 were subjected to the isolation. The results obtained from these experiments are as follows.
1) The 198 strains of Cl. perfringens (identified by Benoki's criterion), that is, the 172 strains from the 171 samples of fish, the 9 strains from the 8 samples of squids, the 4 strains from the 6 samples of shellfish and the 13 strains from the 8 samples of peeled shrimps were isolated (Table 2). Moreover it was revealed as a result of toxicological typing by means of a mouse protection test that every one of those isolates was Type A, and Types from B to F were not detected.
2) For the period from June to September, Cl. perfringens Type A was detected in a high percentage mainly in the unheated specimens of the body-surface of sea-foods, but the microorganisms were not detected in the specimens in October. The rate of detection of Cl. perfringens Type A in the alimentary canal of sea-foods was generally low except a few kinds of fishes (Tables 3 and 4).
3) All the strains of Cl. perfringens Type A isolated from the unheated specimens were heat-sensitive. On the other hand, heat-resistant (100°C, 60min) Cl. perfringens Type A was isolated selectively by applying heating-treatment (80°C, 20min) to the specimens. And the majority of Cl. perfringens (identified by Benoki's criterion) isolated from the heated specimens did not agree with the identification-criterion of Strong et al., especially in the case of heat-resistant strains (Table 5).