Endocarditis caused by Lactobacillus casei subspecies rhamnosus. A case report.

A case of subacute endocarditis in a 66-year-old man with mitral incompetence is described. The causative agent was identified as Lactobacillus casei subspecies rhamnosus, which is a normal commensal in the mouth. Despite the ubiquitous presence of these mouth commensals, this type of endocarditis appears to be rare. It is emphasised that a Lactobacillus species should be considered in cases of clinically obvious endocarditis with 'negative' blood cultures, including 'negative' subcultures following a significant radioactive count in the Bactec system. Suitable media for subculture should be used and incubation for at least 48 hours is required. Other possible reasons for the rarity of this type of endocarditis are discussed.