Improved egg-yolk agar plate medium for the detection of clostridial phospholipase C activity

A new modification of the egg-yolk agar plate medium, an egg-yolk triple-salt medium, is described. The medium incorporates a tryptic soy agar base, yeast extract, D-glucose CaCl2, MgCl2 and ZnSO4. Only in egg-yolk triple-salt medium did all tested phospholipase-C-producing clostridia form a lecitho-vitellin precipitate after overnight incubation; 95.5% formed a high-density precipitate in the new medium as opposed to 6.1%, 6.6%, 10.6% and 20.2% of the isolates not forming a visible precipitate in liver-veal, Lombard-Dowell, McClung and Toabe modified, and "viande-levure" egg-yolk media, respectively, after the same incubation time.