Studies in Bacillus Welchii, with special reference to classification and to its relation to diarrhea.

  • Simonds, J.P.
Date:
September 27, 1915
Catalogue details

Licence: In copyright

Credit: Studies in Bacillus Welchii, with special reference to classification and to its relation to diarrhea. 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.

    24/144 (page 18)
    I found the organism present in 90 to 95 per cent, of the samples of Galveston milk examined. One strain isolated from that source showed an unusually high degree of virulence for guinea pigs. Savage (312) considers the test for B. enteritidis sporogenes of especial value in determining the degree of cleanliness with which the milk was obtained and handled. He stated that there was no evidence of multi- plication of this organism in milk kept at 15° to 18°C. This conclusion was based upon the examinations of the same sample of milk at intervals for spores of the bacillus. He used twenty cubic centimeters of milk dis- tributed in two cubic centimeter quantities in ten tubes heated to 80°C for fifteen minutes, and incubated in a Buchner or Novy jar. Of eighteen samples of milk kept at 20° to 21°C. for eighteen to twenty-four hours, nine (50 per cent.) showed no change in the number of spores of B. welchii; six (33 per cent.) showed an increase (one or two in twenty cubic centi- meters); while three (17 per cent.) showed a decrease (one or two per twenty cubic centimeters). Savage, therefore, considers B. welchii a non- multiplying organism in market milk and therefore a good index to clean- liness at the farm (313). In drawing that conclusion Savage overlooks one very important bio- logic fact with reference to this group of bacteria; namely, that they do not form spores in milk. If there were multiplication of B. enteritidis sporo- genes in the milk it would not show itself in an increase in the number of spores. The multiplication would more probably be indicated by a dimi- nution in the number of spores caused by the germination of some of those originally present. In a few experiments carried out by me this actually appears to take place. On two occasions I found positive tests in three and four tubes out of ten of fresh milk and in only two tubes of each lot from the same milk which had stood for eight hours at room temperature. These tests were made with milk which contained many spores of liquefying bacteria and the tests were not always satisfactory. But they are at least suggestive that a diminution in the number of spores in milk may be associated with an increase in the actual number of B. welchii present. Savage considers milk which shows a positive test in one or none of the ten tubes as good; milk which gives positive test in two or three tubes as unsatisfactory; and milk which shows stormy fermentation in five or more tubes as bad. This is probably a fair statement. In my own rather limited experience it has proved an almost invariable rule that those samples of milk which showed large numbers of the spores of B. welchii also showed visible dirt or other indications of lack of cleanliness in obtaining and handling the milk.