The bacteriological examination of food and water / by William G. Savage.

  • Savage, William George, Sir, 1872-
Date:
1914
Catalogue details

Licence: In copyright

Credit: The bacteriological examination of food and water / by William G. Savage. Source: Wellcome Collection.

Provider: This material has been provided by London School of Hygiene & Tropical Medicine Library & Archives Service. The original may be consulted at London School of Hygiene & Tropical Medicine Library & Archives Service.

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    Such a characterisation is a very wide one and will include a large number of organisms which certainly are not all alike, while many of them will not be identical with the B. coli communis of Escherich. On the other hand these characters will separate the group from the Proteus, Gaertner, Dysentery groups, etc. All the members of this large group have not an equal significance as indicators of excretal contamination so that it is important to carry the classification further. The cultural characters which have been employed for the differentiation of the bacilli of this group are very numerous but in regard to a number of them experience has shown that no differentiation of value is likely to result from their employment and they may be disregarded. Of the differentiation tests still considered by many bacteriologists to be of value the following are the most important:—Production of indol, growth in litmus milk, characters of the growth on gelatine slope, production of fluorescence in neutral red media, Vosges and Proskauer's reaction, and the fermentation of various sugars and alcohols. The value of these tests can be best gauged not only by their ability to adequately differentiate the group as a whole but also by the light they throw upon the distribution of the different members of the group. If by their use differences of distribution are made manifest, so that the finding of the one variety indicates one kind of contamination while the presence of another variety points to a different source of contamination it is obvious that the tests which enable this to be done are of the utmost value. Excreta—human and animal—is the most important form of pollution for which this group is used as a test and the value of these differentiating reactions must largely depend upon how far they satisfactorily differentiate the strains found in excreta from those which have not recently been derived from the animal intestine. The characters of B. coli as found in excreta have been investigated by several workers of whom the following may- be mentioned. Houston1 studied the characters of 101 Coli-like organisms . 1 Local Government Board, Medical Officer's Report, 1902-3, p. 511.