STUDIES ON THE TAKIKAWA'S SO-CALLED PATHOGENIC HALOPHILIC BACTERIA-I

Much attention has been paid on the Takikawa's so-called pathogenic halophilic bacteria, a new type of bacteria suspected to cause food poisoning. It has been only a short period since the investigation started and there are still many problems to be solved, in which pathogenicity of the organisms is still obscure due to the unavailability of susceptible experimental animals. In the present work, effect of various culturing conditions of the organisms upon the lethality for mice has been studied. The results may be summerized as follows: 1. The organisms grew well and gave a high lethality for mice when cultured in a 3% NaCl containing broth which was prepared with casein peptone and fish meat extract. The organisms grew rapidly in such 3% NaCl containing liquid media as the broth composed of meat peptone and fish meat extract, plain peptone water, or peptone-yeast extract medium, nevertheless, the lethality of the cultures were rather low as compared with the above-men-tioned broth culture. 2. As to the NaCl requirement of the organisms, the fastest growth rate was observed in a 3% NaCl broth, while there was no appreciable difference in the lethality for mice between the concentration 2 to 4%. 3. Growth of the organisms and their lethality for mice were varied according to the reaction of medium. Whithin the range of pH 6-8, the higher the pH value, the more rapid in growth or higher in lethality. 4. Presence of glucose in the medium enhanced the growth of the organisms. It was noted that the addition of more than 0.5% of glucose in the medium resulted in decrease in the lethality. 5. In the case of Matsuda strain (serotype XIII), higher lethality was observed in the early stage of culture of the organisms. The organisms lost their lethal toxicity for mice gradually by prolongating the incubation period. 6. Within a range 24° to 37°C., the highest lethality was recorded when the organisms were incubated at 24°C.