[Qualitative und quantitative salmonella investigations and their hygienic valuation in connection with the E. coli titre, demonstrated with examples from the coastal waters of Kiel bight (Western Baltic Sea) (author's transl)]

Abstract

Qualitative salmonella investigations and E. coli titre determinations were carried out in about 4,000 water samples taken from the coastal region of Kiel Bight (Western Baltic) in 1972 and 1973, and evaluated in connection with epidemiological data. Further, about 100 samples were determined quantitatively by the MPN method and set in relation to the E. coli titre. The significance to be attributed to positive salmonella findings particularly in relation to the assessment of risk of infection and as impurity indicators was investigated with reference to this material. A comparison of salmonella findings and E. coli titre showed that with increasing E. coli contamination the proportion of positive salmonella findings also increased (paraboloid curve). Salmonella frequencies and the frequency with which the limiting values of the E. coli titre is exceeded run approximately parallel; the frequency of exceeding a limiting value of E. coli titre of 1.0 and the frequency of salmonella (determination in 100 ml) in sewage laden areas largely coincide. The quantitative salmonella investigations (MPN method) also showed that up to an E. coli titre of 1.0 extremely low salmonella counts only are to be expected (on the average, less than 2/100 ml). With an E. coli titre of 0.1, a marked increase can be seen. A limiting value of 1.0 is proposed for the E. coli titre in coastal waters. Epidemiological data have also shown that an increased risk of infection could not be deduced from positive salmonella findings. According to the present investigations, the value of the information obtained from salmonella findings is small compared with the E. coli titre. Considering the great expense of laboratory investigations, tests for salmonella should be dispensed with in routine examination of water.