Survival of <I>Salmonella typhi</I> in Urban Water System and Coastal Sea Water

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Other Title
  • 都市水系および沿岸海水における腸チフス菌の生残
  • トシ スイケイ オヨビ エンガン カイスイ ニ オケル チョウチフスキン ノ セイザン
  • Survival of Salmonella typhi in Urban Water System and Coastal Sea Water

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Description

Laboratory model experiments were made with the object of clarifying the vital states of Salmonellatyphi in urban water system and coastal sea water, in comparison with those of Salmonella paratyphi B and Shigella sonnei, by adding washed cells of these organisms at a ratio of 10-/ml to samples of sewage, riverwater, estuarine water and sea water. Their survival rates at the mean temperature of the sampleswhen collected were then observed.<BR>Viable cells of S. typhi decreased in number as the time proceeded in each of the water samples. Almost no V-W and S-R variations were found during the period of survival. When the time (days) for reduction of initial population to 1/10 (T1/10) was used as the survival time, index T1/10 at temperaturesbelow 15°C (2.3-7.8) was significantly (P<0.01) greater than those at temperatures above 25°C (0.4-2.2) in each of the water samples used, and it became apparent that T1/10 is inversely correlatedclosely with water temperature. Correlation coefficients between water temperature and T1/10 were-0.73 in sewage, -0.96 in river water, -0.90 in estuarine water and-0.77 in sea water, respectively.It was difficult to ascertain any unique relation between survival and variety of water samples or pH, BOD, COD, C1-concentration, and the number of coliforms and other culturable bacteria, unlikewith the temperature of the samples. Growth or considerable prolongation of the period of survivalwas found in membrane-filtered water samples. Thus, the decrease of viable cells of S. typhi in untreatedwater samples is considered to be mostly due to a competition with-and predation by those micoorganismsnormally living therein, and intensity of these bactericidal actions is considered to be proportional towater temperature. These findings suggest that survival of S. typhi in urban water system is the greatestin the winter season and the most brief in summer, and that in winter when S. typhi is discharged in sewagethe organism may enter the coastal sea and may survive sufficiently long in sea water. With Salmonellaparatyphi B and Shigella sonnei, also, approximately similar results were obtained as with S. typhi, althoughthe test organisms showed a tendency for prolonged survival in the order of S. paratyphi B>S. typhi>S. sonnei. Possibility of transmission of S. typhi to man through shellfish which has been exposed to itin the sea was discussed.

Journal

  • Kansenshogaku Zasshi

    Kansenshogaku Zasshi 48 (11), 426-434, 1974

    The Japanese Association for Infectious Diseases

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