On the etiology of scarlet fever

Abstract

IN January of last year, in a paper in this Journal on " Experimental Scarlet Fever in the Monkey " (1 9 15 *), I gave a preliminary description of a diplococcus isolated from the throats of scarlet fever patients, showed that it produced in monkeys a disease resembling scarlet fever in several respects, and suggested for it the name Dtjdococcus scarlatinm.The object of the present communication is to give a fuller description of this diplococcus, with the technique used for its isolation and identification, and to adduce additional evidence in favour of its causal relationship to the disease. MORPHOLOGY, CULTURAL CHARACTERS, AND CONDITIONS OF GROWTH.Throughout this paper the terms '' ordinary broth " and " ordinary agar " refer to nutrient media prepared in the usual way from meat extract and peptone. The peptone used is either Witte's or another brand prepared from fibrin and is sugar free. Except where otherwise indicated the meat extract is prepared from ox's heart. The reaction of the media is faintly alkaline to litmus. '' Serum broth " and "serum agar" indicate the same media with the addition of 5 to 1 0 per cent. of horse serum. The serum is sterilised by filtration and is added to the broth or melted agar by means of a pipette, the quantity being roughly estimated by the number of drops.In its most typical form, in cultures on serum agar or in serum broth not more than twenty-four hours old, the Biplocoeeus scarlatina? is an oval or oat-shaped coccus measuring about 1.2 p by 0.6 p. It is arranged for the most part in pairs, end to end, and both ends of each member of the pair are distinctly pointed. Shorter and rounder forms are common, measuring about 1 p by 0.8 p. Short chains up to about ten pairs also occur in serum broth. It is non-motile and retains the