Additional tests to differentiate Arcanobacterium haemolyticum and Actinomyces pyogenes.

A commercially available biochemical test panel, commercially available diagnostic tablets and gas-liquid chromatography (GLC) of cellular fatty acids were used to find out whether Arcanobacterium haemolyticum and Actinomyces pyogenes could be further differentiated from each other. Xylitol and alpha-methyl-D-glucoside fermentation, Voges-Proskauer reaction and tributyrate hydrolysis were found to be useful additional tests which differentiated Arc. haemolyticum and A. pyogenes. GLC analysis revealed major differences in the cellular 16:0, 18:2(9,12) and 18:1(9) fatty acid composition of the two species. Especially the Voges-Proskauer test available as diagnostic tablets can be easily performed in clinical microbiology laboratories, in addition to the tests now used to differentiate Arc. haemolyticum from A. pyogenes.