Observations on the Nagler Reaction of some Clostridia

Abstract

NAGLER¹ showed that the surface of colonies of Clostridium oedematiens type A growing on egg-yolk–sheep-blood agar, is covered by a pearly layer. Subsequent investigations by McClung et al. ² and McClung and Toabe³ showed that this phenomenon was not restricted to Cl. oedematiens type A, but was also shown by all types of Cl. botulinum and by Cl. sporogenes, and was more evident if the blood was omitted from the medium. All the Clostridia which show this pearly layer on egg-yolk agar also produce an opalescence within the medium, somewhat similar in appearance to that produced by anaerobes such as Cl. welchii and Cl. bifermentans, which produce lecithinase. Oakley et al. ⁴ showed that cultures and culture-filtrates of Cl. oedematiens type A produce two distinct types of opalescence in egg-yolk emulsions: a diffuse opalescence due to a hæmolytic lecithinase (Cl. oedematiens γ-toxin), and a more confined opalescence due to a lipase (Cl. oedematiens ɛ-antigen). They suggested that the pearly layer also produced by Cl. oedematiens type A might be caused by the lipolytic ɛ-antigen (see also ref. 5). Sussman (personal communication) showed that cultures of Cl. sporogenes were lipolytic when grown on tributyrin agar (‘Oxoid’), and that this organism developed a pearly layer when grown on an agar medium containing triolein.