Catalase-negative Actinomyces neuii subsp. neuii isolated from an infected mammary prosthesis.

In this case report a catalase-negative strain of Actinomyces neuii subsp. neuii is described as the possible causative agent of an infected mammary prosthesis. DNA hybridization studies and 16S rRNA analysis confirmed that the strain belongs to the species Actinomyces neuii subsp. neuii. Since this strain is the first A. neuii subsp. neuii strain reported to be catalase negative, the catalase reaction should no longer be considered a key reaction for the diagnosis of this species but must be interpreted in conjunction with other characteristics.