At present thirty-one serotypes of Diplo- coccus pneumoniae are recognized on the basis of serological reactions, chiefly the Neufeld "Quellung" phenomenon as induced by type-specific immune rabbit serums. Fol- lowing the description of Pneumococcus 1 by Neufeld and Handel (Arb. a. d. k. Gesund- heitsamte, 3^, 1910, 293), Dochez and Gillespie (Jour. Amer. Med. Assoc, 61, 1913, 727) divided the species into Types 1, 2, 3 and a heterogeneous group 4; Cooper, Ed- wards and Rosenstein (Jour. Exp. Med., Jf9, 1929, 461) separated Types 4 to 13 from the strains previously designated as group 4, and later Cooper, Rosenstein, Walter and Peizer (Jour. Exp. Med., 55, 1932, 531) con- tinued the classification to Type 32. Due to marked cross-reactions, it was subsequently decided that Type 6 was identical with Type 26, and that Types 15 and 30 were identical. This resulted in the deletion of the Cooper Types 26 and 30, thus leaving thirty of the original thirty-two types. Type 33 (Wilder) has been described by Walter, Blount, Beat- tie and Cotler (Jour. Inf. Dis., 66, 1940, 181) as a distinct tj^pe; sufficient recognition has been accorded to justify the acceptance of this type, thereby making a total of thirty- one types of the species. In a still more recent publication, Walter, Guevin, Beattie, Cotler and Bucca (Jour. Immunol., Ji.1, 1941, 279) recommend the addition of nine new types and eight subtypes. These, together with new strains reported by Kauffmann, M0rch and Schmith (Jour. Immunol., 39, 1940, 397), if eventually recognized, would make a total of fifty-five types. Eddy still more recently, taking into account all known types, raises the number of recog- nized types to seventy five (U. S. Public Health Repts., 59, 1944, 449-468). Note : Pneumococci, regardless of serolog- ical type, manifest three chief culture phases (or stages) : Mucoid, Smooth and Rough. The Mucoid (M) form corresponds to that previously designated as Smooth (S) and represents the typical phase of the species; Smooth (S) supersedes the earlier term Rough (R); and the present Rough (R) form is a relatively newly described variant. The most frequently observed dis- sociative trend is M -^ S — > R. Serological types are recognizable only in the Mucoid form due to the presence of type-specific polysaccharides in the capsular material; both Smooth and Rough forms are devoid of capsular material but possess species-spe- cific antigens common to all members of the species. Smooth and Rough forms are non- pathogenic, possess distinctive growth characteristics and require special technic for accurate observations. The cultural characteristics given are those of the mucoid and smooth phases only, e.g., see growth in broth. Genus 11. Streptococcus Rosenbach, 1884.* (Mikroorganismen bei den Wundinfectionskrankheiten des Menschen. Wiesbaden, 1884, 22.) Strep. to. coc'cus. Or. adj. streptus pliant; Gr. noun coccus a grain, berry; M.L. mas.n. Streptococcus pliant coccus. Cells spherical or ovoid, rarely elongated into rods, occurring in pairs or short or long chains. Capsules are not regularly discernible but may become conspicuous with some species under certain conditions. Non-motile except a few strains in the enterococcus group. Gram-positive. No pigments are produced with the exception of an occasional strain in Lancefield's groups B and D, which may produce brick-red pigment or yellow pigments under appropriate environmental conditions. A fermentable carbohydrate or polyhydroxy alcohol is necessary for satisfactory growth in artificial media. Growth in broth culture is variable in character. Rough variants may show granular growth that tends to settle out quickly, leaving a clear supernatant. Smooth variants may show uniform turbidity with little tendency to settle out. Such variants may be noted within one species. A pellicle is never formed. Growth on agar surface is usually scanty. Colonies are small, usually less
- Revised by Dr. C. F. Niven, Jr., American Meat Institute Foundation, The University
of Chicago, Chicago, Illinois, in consultation with Professors J. M. Sherman and Harry W. Seeley, Cornell University, Ithaca, New York, November, 1953.
