A Study of Additional Methods of Bacteriological Analyses of Water

Abstract

The success of Standard Methods for the Examination of Water and Sewage (A.P.H.A., 1946) cannot be questioned when its part in the practical elimination of known water-borne enteric disease is realized. Having attained this goal, the question is often raised, "do Standard Methods go far enough?" Could the alltoo-frequent explosive outbreaks of so-called intestinal flu be caused by microorganisms in the water supply not detected by Standard Methods? Furthermore, Chambers (1950) presented data indicating that gas was produced in lactose broth when the population of the coliform group reached a mean value of 170 million per ml of lactose broth; while in brilliant green bile broth nearly 50 per cent greater population is required to produce visible gas. He also pointed out that coliform organisms present may not be revealed by gas production if, in the presence of other organisms, the maximum total population is reached before 170 million coliform organisms per ml are present. Tubiash (1952) showed that nitrates and nitrites in small amounts exert an inhibitory effect on the production of gas by organisms of the coliform group in lactose broth. Since it is established that water from many wells in the north central area contain varying concentrations of nitrates, the question arises as to the adequacy of Standard Methods for determining the safety of well waters. Partially with these facts in mind and partially with the intent of finding a rapid method for detecting not only the coliform group but any enteric organisms which might be implanted in water supplies, two investigations were instigated, one on treated water and one on untreated water. These studies were not conducted simultaneously and will be discussed separately. The work was performed in the laboratory of the Detroit Department of Health with the cooperation of the Bureau of Sanitary Engineering.