minor antigen (reacting feebly) in common with Shigella dysenterine. Source: Isolated from the stools of dysen- tery patients. Habitat: Found in cases of human dysen- tery, especiall}' in Europe; relatively un- common. 3. Shigella arabinotarda Christensen and Gowen, 1944. (See Large and Sankaran, Jour. Roy. Army Med. Corps, 63, 1934, 231; and Sachs, Jour. Roy. Army Med. Corps, 80, 1943, 92; Christensen and Gowen, Jour. Bact., 47, 1944, 171.) a.rab.i.no.tar'da. M.L. arabinosuni arab- inose; L. adj. tardus late; M.L. adj. ara- binotardus (probably intended to mean) producing a late or slow fermentation of arabinose. These organisms, frequently referred to as the Large-Sachs Q-group, comprise six recognized serotj^pes, which are known as Q 771, Q 1167, Q 1030, Q 454, Q 902 and 599-52; there is little doubt that Dudgeon and Urquhart's para-shiga is included (Med. Res. Council Special Report Series No. 40, 1919). The morphology and cultural characters on agar, gelatin, broth, potato and milk are identical with those of Shigella dysenteriae. Ladole not produced (except by serotype Q902). Hydrogen sulfide not produced. Acid from glucose, galactose, fructose, sorbitol and arabinose (slowlj^- No acid from lactose, mannitol, dulcitol (except serotype Q 1030) or rhamnose (except sero- type Q902). Nitrites produced from nitrates. Trimethylamine not produced from tri- methylamine oxide. Aerobic, facultatively anaerobic. Temperature relations: Optimum, 37° C. No growth at 45° C. Antigenic structure: Each type possesses a type-specific particular O antigen and lacks a group antigen; therefore there is no cross reaction with other species. There is a thermolabile capsular L antigen which can mask the O agglutination; thus diagnostic tests are best with broth cultures with destruction of L antigen. Source: Found only in the stools from cases of dysentery. Habitat: Relatively" imcommon in out- breaks of dysentery due to Shigella flexneri. 4. Shigella boydii Ewing, 1949. (Jour. Bact., 57, 1949, 634 and 635.) boyd'i.i. M.L. gen. noun boydii of Boyd; named for Col. J. S. K. Boyd, the English bacteriologist who has made a special study of dysentery organisms. Rods. Non-motile. Some strains of sero- type 2 may be encapsulated (Ewing). Gram- negative. Gelatin: No liquefaction. Indole produced by serotypes 5, 7 and 11. Hydrogen sulfide not produced. Acid but no gas from mannitol (except for certain strains of serotypes 3, 6 and 10), glucose, arabinose and occasionally from sucrose and maltose. Nitrites produced from nitrates. Antigenic structure: Shigella boydii is dis- tinguished from Shigella flexneri by possess- ing a type-specific major O antigen and by lacking a group antigen. Some have minor antigens, which fact explains their serologi- cal relationships. Certain strains of Shigella boydii 2, 3, 5 and 7 may have K antigens, particularly antigen L, which masks the O agglutination. In this case the agglutination should be made in tubes with boiled cultures (Mad- sen). To determine the serological type, un- absorbed anti-boydii 1, 2, 3 and 5 sera are used, but anti-boydii 4 serum should be absorbed with Shigella alkalescens and serum 6 with Shigella sonnei in phase II. With encapsulated Shigella boydii 2, a serum may be prepared which causes swelling of the capsule of an organism of type 2 when a capsule is present. There are eleven serotypes, which are represented by the following recognized strains: 170, P288, 5DI, P274, P143, D19, Lavington, 112, 1296/7, 430 and 34. Relationships to other species: Shigella boydii 1 has antigenic relationships with serotype 4, and Shigella boydii 3 with sero- type 6. However by far the most important serological relationships are those of Shigella
