The growth and survival of Vibrio cholerae O-1 and Vibrio cholerae non O-1 in foodstuffs, especially in shellfish was studied in order to cast some light on the ecology of cholera epidemic.
Alteration in the number of Vibrio cholerae O-1 and Vibrio cholerae non O-1, stuck to raw fish and raw meat, drinks (cola, alkali ion drink, milk, coffee) and soy sauce was observed in a settled temperature and whether cholera had accumulated in short-necked clams in artificial sea water contaminated with Vibrio cholerae O-1 or Vibrio cholerae non O-1 was examined. In this study, the same experimental procedure was pursued concerning the different strains of cholera ; Vibrio cholerae O-1 and Vibrio cholerae non O-1.
The following results were obtained :
1) Within 24 hours, the number of Vibrio cholerae O-1 or Vibrio cholerae non O-1 stuck to raw fish or raw meat was almost invariable at 4°C, 10°C, 16°C and 30°C.
After 48 hours, the number of Vibrio cholerae O-1 or Vibrio cholerae non O-1 stuck to raw fish was invariable, though the numbers of both strains stuck to raw meat decreased. Regarding the rate of decrease, Vibrio cholerae non O-1 was slower than Vibrio cholerae O-1.
2) Vibrio cholerae O-1 and Vibrio cholerae non O-1 ceased to exist within 30 min in soy sauce of high salt concentration and within 30 min in cola and alkali ion drink of high acidity. On the other hand, Vibrio cholerae O-1 in coffee ceased to exist within 24 hours at 4°C and 16°C.
3) When short-necked clams were placed in artificial sea water contaminated with Vibrio cholerae O-1 or. Vibrio cholerae non O-1, the organisms survived and accumulated within the short-necked clams.

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Studies of El Tor cholera Vibrio have been studied by a great many workers in the past.
Unfortunately, however, the biological study of El Tor cholera Vibrio is still meager. And the growth and survival of El Tor cholera Vibrio in foodstuffs is a important problem of infection. Therefore, several experiments were conducted. The first experiment was made with the object of clarifying the vital time of El Tor cholera Vibrio in cola, alkali ion drink, milk, coffee, peptone solution and soy sauce. The second was made, increase or decrease of the number of El Tor cholera sticking to raw fish and raw meat in settled temperature. The third, whether El Tor cholera Vibrio was accumulated in short-necked clams in artificial sea water which was contamined with El Tor cholera Vibrio.
Factors influencing the survival of El Tor cholera Vibrio were studied. Results obtained were followings.
1) El Tor cholera Vibrio became extinct within 5 min in soy sauce of a high salt concentration and within 15 min in cola and alkali ion drinks of high acidity. But they did not extinct up to 60 min in milk, coffee and peptone solution.
2) El Tor cholera Vibrio sticking to raw fish or raw meat survived longer at 8°C than at 16°C or 24°C. The number of surviving El Tor cholera Vibrio increased temporally but decreased lator. The number of its increase was positively corelated with the degree of environmental temperature.
In addition, when short-necked clams were placed in artificial sea water which had been contaminated with El Tor cholera Vibrio, it was found that organisms were accumulated and survived within short-necked clams.

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Laboratory model experiments were made with the object of clarifying the vital state of El Tor cholera vibrio (ETCV) in coastal sea water, sewage, city water and river water, comparing the results with those obtained in phosphate buffer solution and sterilized water. Their survival rates were calculated at the water temperature at which the samples were collected in summer and winter. Into the sample water, ETCV was added at the rate 10⁵/ml.
Additional experiments were performed in 0.1% Peptone solution to determine the effects of NaC1 concentrations, pH and temperature on the survival rate. The results obtained were as follows:
1) As the time elapsed, the number of surviving ETCV decreased in all water samples with the exception of sea water. When the interval of decrease (in days) from its initial population to its 1/10 (T 1/10) or 1/100 (T 1/100) level was used as the survival time, the indices T 1/10 or T 1/100 at 25°C were greater than those at 15°C.
2) The relation between the survival rate and the number of coliform or other culturable bacteria was inverse.
3) ETCV multiplied fairly well in 2 and 3% NaC1 solution, whereas the multiplication was poor in 1% and 4%.
4) It was unsuccessful to clarify the connection between the ETCV survival rate and pH, BOD or COD. However, in Peptone solution, the multiplication of ETCV was more pronounced in neutral environment and in acid or in alkali.

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The purpose of these experiments was to elucidate the relation between the behavior of El Tor cholera Vibrio (ETCV) to antibiotics and that of Escherichia coli (E. coli) as one of intestinal bacterial floras.
In the presence of several antibiotics equivalent to a minimum inhibitory concentration (MIC) for ETCV, ETCV was mixed with two strains of E. coli which were different in sensitivity to antibiotics. The change of the viable cells of each bacterium was then observed.
The results obtained were as follows :
1) ETCV on these experiments was not very sensitive to polymyxin B (PL) and colistin (CL).
2) In the mixed cultures with antibiotic-resistant E. coli containing ampicillin (ABPC), cephalothin (CET), amikacin sulfate (AMK) and chloramphenicol (CM), an upward tendency of MIC for ETCV was observed.
3) When the inoculum size of E. coli was as much as, or more than that of ETCV in the mixed cultures containing ABPC, sensitivity of E. coli to ABPC was the factor which influ-enced the behavior of ETCV during a period of six hours.
4) When the inoculum size of E. coli was as much as, or less than that of ETCV in the mixed cultures containing CET, the difference of antibiotic-resistance between the two strains of E. coli influenced the growth of ETCV.
5) In the mixed cultures containing CM, the difference of antibiotic-resistance between the two strains of E. coli influenced the growth of ETCV.
6) In the mixed cultures with the standard strain of E. coli containing tetracycline (TC), the growth of ETCV was inhibited for a long period. But in the mixed cultures with the antibiotic-resistant strain of E. coli, the growth of ETCV had a tendency to be inhibited in an inverse proportion to the inoculum size of E.coli.
7) In the mixed cultures containing PL, ETCV showed almost the same behavior independently of the strain and inoculum size of E. coli.

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