Abstract
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.
