Fermentation Information and Courses from MediaLab, Inc.

Key reactions for the identification of Clostridium septicum are demonstrated in the two quadrant plates shown in the images to the right. Included in the upper image are reactions for milk (casein) proteolysis (12 o'clock quadrant), glucose fermentation, DNAse hydrolysis, and starch hydrolysis respectively reading clockwise. The media in the quadrant plate shown in the lower image include gelatin hydrolysis (2 o'clock quadrant) and fermentation of each of mannitol, lactose, and rhamnose respectively, reading clockwise. Milk (casein) hydrolysis and glucose fermentation are key reactions for the identification in the upper plate, including no proteolysis of milk, fermentation of glucose (yellow red color along the inoculation streak), positive DNAse (reddish clearing around the streak) ,and a negative reaction for starch. Key reactions in the lower plate include hydrolysis of gelatin, fermentation of lactose (yellow pigment), and negative reactions for mannitol and rhamnose (no pigment). Most strains of C. perfringens hydrolyze starch and produce proteolysins of milk, the key reactions that distinguish C. septicum (negative). Reactions to the other tests do not distinguish between the two.

Although not performed that often, the following tests are useful in separating E. corrodens from other closely related members of the HACEK group: KIA showing an alk/alk reaction; Glucose fermentation (-); Reduction of nitrates to nitrites (+); Production of indole (-); Ornithine decarboxylase (+) The positive nitrate reduction reaction eliminates Cardiobacterium hominis, Kingella kingae and other Kingella species. The positive ornithine decarboxylase reaction eliminates Kingella denitrificans (which also denitrifies nitrate to nitrogen gas, a reaction negative for E. corrodens). Eikenella corrodens is asaccharolytic, whereas most other closely related species produce acid from one or more carbohydrates.