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 thi
s strain is the first A. neuii subsp. neuii strain reported to be catalase
negative, the catalase reaction should oct longer be considered a key react
ion for the diagnosis of this species but must be interpreted in conjunctio
n with other characteristics.