The origin of some of the streptococci found in milk / by L.A. Rogers and Arnold O. Dahlberg, Dairy Division, Bureau of Animal Industry.

  • Rogers, L. A. (Lore Alford), 1875-1975
Date:
[1914?]
Catalogue details

Licence: In copyright

Credit: The origin of some of the streptococci found in milk / by L.A. Rogers and Arnold O. Dahlberg, Dairy Division, Bureau of Animal Industry. Source: Wellcome Collection.

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    more cows were rendered useless. There was no apparent connection between the two epidemics except that they occurred at about the same time. We may assume that these epidemics originated in one of two ways, either of which must admit more or less variation in phys¬ iological reactions from the original type. It may be possible that the udders of one or more cows may have become infected by some of the streptococci coming originally from the mouth, intestines, or other sources. Under the influence of its new environment this organism may have acquired pathogenic properties sufficient to produce the symptoms observed in mammitis. Heinemann has shown that pathogenicity is a property readily acquired when ordinary streptococci are grown in ani¬ mals.1 If these infecting organisms came from the mouth, the intes¬ tines, or the milk they must have acquired in a comparatively short time an entirely new set of biochemical reactions in addition to a variation in pathogenicity. On the other hand, we may assume with much more appearance of reasonableness that the infection spread from a single infecting cell or aggregate of similar cells which already possessed patho¬ genic powers and general characters identical with those we have found to be characteristic of the udder organisms. This assumption is in accord with the established fact that streptococci from pathological lesions in general have similar biochemical reactions. If the infection in these two cases came from various sources, it must follow that growth under similar conditions would produce uniform fermentation reactions in a short time, a view held by Walker, who maintains that these reactions may be varied almost at will and can only indicate the latest habitat of the culture.2 If the infection came from a single cell, there must have been some variation, since the fermentation reactions were not identical at the time of this isolation. In Table X are shown the varieties of nonliquefying udder cultures and the number occurring in each of the two herds. There were seven varie¬ ties in all. The most numerous one ferments dextrose, saccharose, and lactose only and occurred 24 times, equally divided between the two herds. The next most numerous variation differed from the first in failing to ferment saccharose and occurred 8 times. A third variation fermented mannite in addition to dextrose, saccharose, and lactose and occurred 4 times. The remaining four varieties evidently occur only once or twice in every 40 cultures. Viewed from any standpoint it is evident that these organisms are subject to variation from the type, but these variations are not of sufficient magnitude or frequency to detract from the value of the physiological reactions as a means of establishing true species. 1 Heinemann, P. G., The pathogenicity of Streptococcus lacticus. Jour. Infect. Diseases, v. 4. no. 1, p. 87-92. 1907. 2 Walker. E. W. A., On variation and adaptation in bacteria, illustrated by observations upon strepto¬ cocci. with special reference to the value of fermentation tests as applied to these organisms. Proc. Roy. Soc. [Eondon], s. B. v. 83. no. 567. P. 541-558. 1911*