Practical bacteriology, microbiology and serum therapy (medical and veterinary) : a text book for laboratory use / by A. Besson ; translated and adapted from the fifth French edition by H.J. Hutchens.

  • Besson, Albert, 1868-
Date:
1913
Catalogue details

Licence: In copyright

Credit: Practical bacteriology, microbiology and serum therapy (medical and veterinary) : a text book for laboratory use / by A. Besson ; translated and adapted from the fifth French edition by H.J. Hutchens. Source: Wellcome Collection.

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    number of samples of typhoid-infected waters and it may altogether mask the presence of the typhoid bacillus. Whenever a colon bacillus is isolated from a sample of water its charac- teristics should be carefully studied. If these agree in all details with those of the typical colon bacillus of Escherich (and the author attaches considerable importance to the rapidity with which milk is coagulated) and more particu- larly if the strain isolated prove to be pathogenic to guinea-jugs (using O'5-l c.c. of a 24-hour broth culture intra-peritoneally) no hesitation need be felt in expressing an adverse opinion upon the water. The coincident occurrence of bacteria associated with putrefaction renders it still more probable that the pollution is excretal in origin. Great importance is to be attached to the inoculation of animals with organisms isolated from water and grown at 37° C. This experiment should never be omitted before coming to a final conclusion. Vincent attaches some importance to the numbers in which the colon bacillus is found in a water and in his opinion a water which only contains 10 to 50 colon bacilli per litre may be regarded as good in quality. For the purpose of ascertaining the number present he adopts the dilution method using broth containing 070 per 1000 of carbolic acid. [An opinion upon a water must be based upon a number of data of which the occurrence of the colon bacillus is merely one. The numbers in which the colon bacillus or colon-like bacteria are present is, of course, a matter of importance but its importance depends upon other factors : for these numbers will vary according to the source of the water, and a number which would be sufficient to condemn absolutely a deep well water would be disregarded in an upland surface water. In effect an absolute standard cannot be fixed ; a mere laboratory examination of the water without a full knowledge of its source is in the vast majority of cases of little or of no value. The real value of a bacteriological examination will depend upon the consideration of all the facts both as to source, method of collection, mode of transit, and the nature and number of the various micro-organic species present; and the interpretation of these data is a matter requiring considerable knowledge and experience. Moreover it is now agreed by all who are in a position to express an opinion, that before a reliable conclusion as to the purity of a water can be arrived at the laboratory examination must be systematic extending over a period sufficient to cover all possible or likely sources of contamination.] C. Systematic examination for certain pathogenic organisms. During an epidemic of enteric fever or cholera or if a number of cases of anthrax occur, the specific organisms should be systematically sought for. The pathogenic organisms which have most frequently to be isolated are the colon bacillus, the typhoid bacillus, the pneumobacillus, the anthrax bacillus and the cholera vibrio. The methods to be adopted in each of these cases have alreadv been described in the chapters devoted to a detailed consideration of these organisms. 3. Houston’s method of water examination.1 Houston some years ago introduced a method for the bacteriological examination of water which in the United Kingdom and in many parts of the Dominions beyond the Seas has now superseded all others. The sample of water is examined with a view to determining 1. The total number of organisms present. 1 This sub-section has been added.