dispar (in part) Andrewes, Lancet, 194, 1918, 560 (see Shigella dispar); Bacterium sonnei Levine, Jour. Inf. Dis., 27, 1920, 31; Weldin, Iowa State Coll. Jour. Sci., 1, 1927, 182; Proshigella sonnei Borman, Stuart and Wheeler, Jour. Bact., 48, 1944, 363.) son'ne.i. M.L. gen. noun sonnei of Sonne; named for Dr. Carl Sonne, who worked with this organism. Rods. Non-motile. Gram-negative. Gelatin: No liquefaction. Agar colonies : Cultures dissociate readily, and after the first transfers variants develop which modify their appearance and anti- genic structure. Three, and sometimes even four, colony forms may develop (Wheeler and Mickle, 1951). Phase I colony: circular, gray, convex, 2 to 4 mm in diameter, entire, smooth, glistening; readily emulsified in normal saline. Phase II colony: granular, glistening, 5 mm in diameter, translucent edge, irregular; readily emulsified in normal saline. Goebel et al. describe phase Ilr colonies similar to the phase II colonies of Wheeler and phase lis colonies, small (1 to 2 mm in diameter), smooth and glistening, which have a distinctive antigenic struc- ture. The organisms of these colonies emul- sify readily (Baker and Goebel, 1949). The colonies in phase II of Shigella sonnei do not grow on certain selective media, SS agar or desoxycholate agar (Leifson). Broth: Many strains make the medium turbid just as do cultures oi Shigella flexneri; some form heavy flakes by spontaneous agglutination of the cells. In broth cultures the variation S -^ R is common. These colonies are flat, 8 to 10 mm in diameter, gray, undulate, rugose with irregular, some- times lobate, edges. Spontaneous agglutina- tion occurs in normal saline. Milk: Coagulated in 4 to 30 days. Indole not produced. Acid but no gas from lactose (2 to 30 days) or sucrose (10 to 40 days) . Acid from glucose, fructose, maltose, galactose, mannitol, arabinose, raffinose and rhamnose in 24 hours. Dulcitol, inositol, adonitol and xylose usually not attacked. Nitrites produced from nitrates. Trimethylamine produced from tri- methylamine oxide. Aerobic, facultatively anaerobic. Optimum temperature, 37° C. Growth at 45.5° C. Antigenic structure: Antigens of phase I, extracted in an aqueous solution of glyc- erol, and those of phase lis, extracted in a 50 per cent solution of pyridine, are protein lipocarbohydrates of a nearly similar chemi- cal composition. The serum prepared with living organisms in phase I agglutinates bacteria in phases I and II, while that prepared with organisms in phase II agglutinates only bacteria in phase II. The agglutination of phase II organisms by the antiserum of phase I is explained by the presence of bacteria under- going phase II mutation. The antiserum pre- pared with the organisms of phase lis agglu- tinates the organisms of phase lis and of phase llr but has no effect on the organisms of phase I. On the contrary, the antigens of phases I and lis are strongly specific (Goebel). Shigella sonnei in phase II has antigenic components common to Shigella boydii 6, Shigella boydii 4, Shigella alkalescens and Shigella dispar. Distinctive characters: Appearance of broth cultures and of agar colonies; slow fermentation of lactose. Comments : Some strains of Shigella sonnei do not ferment lactose, make milk alkaline or ferment xylose or rhamnose in 24 hours. Other strains which do not attack rhamnose have the same biochemical reactions as Shigella boydii 6 (D 10) . The cells of these colonies in phase I and phase II are agglu- tinated by the anti-sonnei serum absorbed by D 19 (Rubinsten and Pi6chaud, Ann. Inst. Past., 82, 1952, 770). Hammarstrom (Lancet, 1, 1947, 102; and Acta med. Scand., ISS, 1949, Suppl. No. 223) has classified the strains of Shigella sonnei into 68 types by means of eleven specific bacteriophages and one non-specific bacteriophage tending to show whether the culture is in the typable form, R. Types 3 and 5 are the most common, then types 7, 8, 12, 16, 53 and 19. This method is of great epidemiological value. Source: Isolated from feces in cases of dysenterj' or gastroenteritis; also isolated from drinking water (Green and MacLeod, 1943).
