tinguished from Streptococcus faecalis by serological type-specificity. Litmus milk: Acidified, curdled and pep- tonized. The proteolysis of the milk is usually characteristic in showing digestion down one side of the tube. Litmus com- pletely reduced before curdling. Old labora- tory strains tend to lose their ability to peptonize milk. Gelatin liquefied. 16b. Streptococcus faecalis var. zy mo- genes (MacCallum and Hastings, 1899) Mattick, 1947. {Micrococcus zymogenes MacCallum and Hastings, Jour. Exp. Med., 4, 1899, 521; Streptococcus zymogenes Hol- land, Jour. Bact., 5, 1920, 226; Mattick, Proc. Fourth Internat. Cong, for Micro- biology, Copenhagen, 1947, 519.) zy.mo'ge.nes. Gr. noun zyme leaven, fer- ment; Gr. V. gennaio to produce; M.L. adj. zymogenes ferment-producing. This variety was regarded as a separate species. Streptococcus zymogenes, in the Manual, 6th ed., 1948, 327, but it is be- lieved that the differences are not sufficient to warrant species distinction. This variety possesses the same characteristics as Strep- tococcus faecalis except as given below. It is a member of the enterococcus group and Lancefield's group D. It can not be dis- tinguished from Streptococcus faecalis by serological type-specificity. Action on blood: Broad zoned hemolysis (beta hemolytic). An acid-labile soluble hemolysin is produced, but it is difficult to demonstrate under the usual conditions of testing. Litmus milk: Acidified, usually curdled, with complete reduction of the litmus be- fore curdling. May or may not peptonize. The proteolytic strains show changes in litmus milk similar to those effected by Streptococcus faecalis var. liquefaciens. Gelatin may or maj^ not be liquefied. 17. Streptococcus durans Sherman and Wing, 1937. (Jour. Dairy Sci., 20, 1937, 165.) du'rans. L. part. adj. durans hardening, resisting. Spherical to ovoid cells elongated in di- rection of the chain; 0.5 to 1.0 micron in diameter. Occur mostly in pairs or short chains. Serology: Belongs to Lancefield's group D. Many serological types are known to exist. No distinctive separation of the serological types from those oi Streptococcus faecalis and its varieties, although some broad divisions can be made (Sharpe and Shattock, Jour. Gen. Microbiol., 6, 1952, 150). Action on blood: Hemolytic (beta), but the zones of hemolysis are generally less ex- tensive than those produced by Streptococ- cus faecalis var. zymogenes. Soluble hemoly- sin difficult to demonstrate. Abundant growth with the production of uniform turbidity and heavy sediment in broth media containing fermentable carbo- hydrate. Not fibrinolytic. Temperature relations : Growth at 10° and 45° C. Survives 60° C. for 30 minutes. Tolerance tests: Same as iox Streptococcus faecalis . Litmus milk: Acidified, usually curdled, with litmus reduction after curdling. No proteolysis. Final pH in glucose broth, between 4.0 and 4.5. Acid from glucose, maltose and lactose. Trehalose and salicin may or may not be fermented. Ferments glycerol only aerobi- cally. Sucrose and mannitol rarely fer- mented. Arabinose, raffinose, inulin and sorbitol not fermented. No polysaccharide synthesized from sucrose. Starch or gelatin not hydrolj'zed. Sodium hippurate may or may not be hydrolyzed. Esculin split. Ammonia produced from arginine. Tyrosine is decarboxylated to yield tyramine and carbon dioxide. Distinctive characters: As a member of the enterococcus group, this species is closely related to Streptococcus faecalis and its varieties. Other than its hemolytic properties, this species may be difficult to distinguish from some cultures now classi- fied as Streptococcus faecalis. However, in contrast to the typical Streptococcus fae- calis, this species fails to reduce litmus be-
