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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    \ represent the normal streptococci of milk but rather those which would usually be distinguished as indicating contamination from infected udders or fecal sources. Fifty-one cultures were isolated from 19 samples of milk obtained by milking directly into sterile test tubes. The cows from which these samples were obtained represented all gradations of infected udder from occasional evidence of garget to acute mammitis. Part of these were in the Dairy Division herd at Beltsville, Md., and the remainder in the herd on the Naval Academy farm at Annapolis, Md. One hundred and fourteen cultures came from 56 samples of cow manure obtained> with the exception of a few from Troy, Pa., at the Dairy Division farm and at the dairy of the Government Hospital for the Insane at Wash¬ ington. Thirty-nine cultures were made from the mouths of animals at the Dairy Division farms. With the exception of one culture obtained from the mouth of a mule, all of these cultures were of bovine origin. In Table II the origin of the culture is indicated by M for milk, U for udder, F for feces, and B for mouth. The sample from which the culture was secured is indicated by a number following the letter. For instance, “F15” represents sample of feces No. 15. This will enable the reader to determine the origin of each culture and the number of cultures from each sample. MORPHOLOGY OF THE CULTURES While it is generally recognized that there is little morphological basis for subdivisions of the streptococci, reference is frequently made to certain types of cells. Stowell, Hilliard, and Schlesinger,1 in selecting streptococci from milk for comparison with those isolated from the human throat, rejected diplococci and the oval-chained form which they designate as the Streptococcus lacticus of Kruse or the Bacillus lactis acidi group, respectively. In selecting our cultures no attention was paid to morphology beyond determining that it was a coccus apparently dividing in one plane, with the exception of those from milk, which were not accepted if they did not form chains of at least 8 or 10 cells. The morphology of nearly all cultures was determined by examination of specimens stained with gentian violet. Camera-lucida drawings were made using a Leitz 3 mm. objective and No. 18 ocular, a combination which gave a magnification of 2,400 diameters at the ocular, or 4,800 diameters on the drawing board. Sufficient light to give a clear image was obtained by using a special arc light with a copper-sulphate ray filter. Preliminary studies showed that the medium on which the culture was grown had an appreciable influence on both the size and the form of the cell. This is shown in figure 1, which is reproduced from camera-lucida drawings of typical cultures grown on various media. Milk gave quite l Stowell, E. C., Hilliard, C. M.. and Schlesinger, M. J., A statistical study of the streptococci from milk and from the human throat. Jour. Infect. Diseases, v. 12, no. 2, p. 144-164. 1913.