Use of second-line biochemical and susceptibility tests for the differential identification of coryneform bacteria

Abstract

Objective: To investigate which 'second-line' biochemical and susceptibility tests could be used for the differential identification of coryneform bacteria (Actinomyces, Arcanobacterium, Brevibacterium, Corynebacterium, Dermabacter, Rothia, Turicella). Methods: Tests used for the diagnosis of certain Gram-negative rods and nocardiforms: growth in 10% NaCl; production of β-galactosidase, arginine dihydrolase, ornithine and lysine decarboxylase, γ-glutamylaminopeptidase, and methanethiol; hydrolysis of tributyrin, casein, tyrosine, and starch; assimilation of carbohydrates in the API 20 NE system; gas-liquid chromatography for end products of glucose metabolism, and susceptibility to antimicrobials used for diagnostic purposes. Results: Some tests proved useful for the differentiation within the genus Corynebacterium (e.g. growth in 10% NaCl, tyrosine hydrolysis, furazolidine and 0/129 susceptibility), while others differentiated only between genera (e.g. methanethiol formation, bacitracin susceptibility). Conclusion: Second-line tests can be of use for the differential identification of coryneform bacteria.