Determ. Bact., 1901, 228; Castellani and Chalmers, Man. Trop. Med., 3rd ed., 1919, 935.) dy.sen.te'ri.ae. Gr. noun dysenteria d^'senter}-; ^NI.L. gen. noun dysenteriae of dysentery. Rods, 0.4 to 0.6 by 1.0 to 3.0 microns, oc- curring singly. Non-motile. Gram-negative. Gelatin: Surface growth. No liquefaction. Agar colonies: Circular, 1.0 to 1.5 mm in diameter, raised, gray, opaque, shiny, en- tire. After 48 hours there is spreading, and the centers of the colonies become thick- ened. Broth : Slightly turbid in several hours, in- creasing after 18 hours to a homogeneous turbidity. Litmus milk: Slightly acid, slowly becom- ing slightlj^ alkaline. Potato: Growth shinj^ slowly turning brown. Indole not produced. Hydrogen sulfide not produced. Acid but no gas from glucose, fructose, galactose, rafhnose and sometimes from glycerol (positive reaction with Stern's medium). Xylose, maltose, sucrose, manni- tol, dulcitol, arabinose, rhamnose, salicin and adonitol not attacked. Kligler's medium: Red slope; yellow butt; no gas. Nitrites produced from nitrates. Trimethylamine not produced from tri- methylamine oxide. Catalase not produced. Aerobic, facultatively anaerobic. Optimum temperature, 37° C. No growth at 45° C. Antigenic structure: The antigen of Shigella dysenteriae consists of a non-anti- genic phospholipid and an antigenic toxic protein together with a polj'saccharide re- sponsible for the serological reactions (Boivin and Mesrobeanu, 1937; Morgan and Patridge, 1940) . All strains have an identical antigenic structure; they also have a minor antigen, identical with that of Shigella ambigua Weldin, which does not interfere with slide agglutination. Toxin production: Among the dysentery bacilli only Shigella dysenteriae produces an active exotoxin in liquid media which can be changed into an anatoxin (toxoid) by the action of formalin and heat (Ramon, Dumas and Said Bilal, 1926). Pathogenicity: Avirulent but toxic for man causing epidemic bacillary dysentery. This is the only dysentery bacillus patho- genic for laboratory animals (rabbits, mice, monkeys and dogs), producing lesions simi- lar to those found in man. Dissociation: Dissociates spontaneously into S and R variants. The latter, which lack the antigen, can produce an active exo- toxin. Source: Isolated from widespread epi- demics of dysentery. Habitat : A cause of dysentery in man and monkeys. Found only in feces of the sick. 2. Shigella schinitzii (Weldin and Levine, 1923) Hauduroy et al., 1937. {Shi- gella parashigae Remlinger and Dumas, Ann. Inst. Past., 29, 1915, 493; Bazillus Schmitz, Schmitz, Ztschr. f. Hyg., 84, 1917, 449; Bacillus dysenteriae "Schmitz", Murray, Jour. Roy. Army Med. Corps, 31, 1918, 257; Bacillus ambiguus Andrewes, Lancet, 194, 1918, 560; Bacterium schmitzii Weldin and Levine, Abst. Bact., 7, 1923, 13; Shigella ambigua Weldin, Iowa State College Jour. Sci., 1, 1927, 177; Hauduroy et al.. Diet. d. Bact. Path., 1937, 496.) schmit'zi.i. M.L. gen. noun schmitzii of Schmitz; named for Dr. K. E. F. Schmitz of Roumania. Morphology and cultural characters on agar, gelatin, broth, milk and potato are identical with those of Shigella dysenteriae. Indole always produced. Hj^drogen sulfide not produced. Acid from glucose, galactose, fructose, maltose and rhamnose; irregular acid pro- duction within 4 days from arabinose. No acid from lactose, sucrose, mannitol, dul- citol, sorbitol, salicin, xylose or glycerol (negative reaction with Stern's medium). Nitrites not produced from nitrates. Trimethylamine not produced from tri- methylamine oxide. Catalase not produced. Aerobic, facultativeh^ anaerobic. Temperature relations: Optimum, 37° C. No growth at 45° C. Antigenic character: Possesses a major antigen specific to this species only and a
