Streptococci Occurring as Diplococci in Rats. (M. norvegicus)

Abstract

The most striking features of the following infection encountered in two rats are the presence in the affected tissues of numerous diplococci morphologically resembling the meningococcus; diplococcemia, and the presence of a marked subcutaneous edema. While the micrococci occur mainly in pairs, occasionally short chains may be detected in smears from the tissues. They take the ordinary aniline dyes readily, and retain the stain in Gram's method. They grow readily upon transfer from the tissues to H-1 agar slants. Their biochemical characters, as far as determined, may be summed up briefly as follows: Upon +I agar slants, in 24 hours, at 370 , pin-point to 0.25 mm. circular, white colonies with thin even edges appear. In 48 hours the colonies are larger and finely granular under low magnification, with finely notched or smooth edges. Colonies upon +1 rabbit's blood-agar plates are surrounded by a zone of hemolysis; the growth is more delicate upon rabbit's blood-agar slants than upon plain agar. Cultures may be kept viable for months on rabbit's blood agar, but not so on plain agar. Slight flocculent growth in -fi broth. Delicate white growth, without liquefaction, in +1.5 gelatin (18-250) in the case of culture 2,854; no growth in the case of culture 22,398. No visible change in -|-i milk during seven days' growth. Acid is produced in -h 1 litmus broth, containing 1 per cent dextrose, levulose, saccharose, maltose, and galactose; mannite and inulin are not fermented. Culture 2,854 produces acid from lactose while 22,398 does not. As usual the growth is very much more luxuriant and longer chains are formed in the media containing fermentable carbohydrates. Experimentally the micro-organisms were pathogenic to white rats but not to guinea-pigs nor rabbits. Notes on the original infected rats read as follows: