Abstract
The author has discovered a new strain of a psychrophile showing a high activity of histidine decarboxylase, which is different from causative organisms for food poisoning reported so far. The author considers that this strain belongs to Citrobacter group according to the classification by Kauffmann (1956) and Edwards et al (1962) on the basis of its behaviours concerning morphology and biochemical characteristics. The author denominated this bacteria Citrobacter YK. It can not grow at 37°C. Its optimal temperature for growth is 20°C, and it can grow even at 4°C from which the word psychrophile itself formulates a good definition. The author has implanted this bacteria in an extract of tuna and also in dried mackerel flesh and obsereved no growth without any histamine production at 37°C. A paper chromatography indicated the amount of histamine produced at various temperatures within the limit of 27°C-4°C to be 3.2mg/g. According to the facts stated, the author confirmed that this bacteria is a causative bacteria of the allergy-like food poisoning. As a report indicating the presence of a psychrophile which produces histamine has not been published, this discovery will be of a significance. The author considers that the fact is important from the point of food hygiene, as the problem of coldchain market has come to be discussed in their country.
