Background: Propionibacterium acnes, a gram positive, anaerobic, skin commensal bacillus, is too often considered a biologic fluid contaminant, of blood cultures in particular. Its implication has been shown in various infections, including brain abscess, ocular infections, osteitis, and acne. It is also the cause of infective endocarditis (IE).
Methods: Retrospective, observational study of 11 patients with P. acnes IE, hospitalised between 1993 and 2001 at the Louis Pradel Hospital, Lyon-Bron, and review of 20 published cases.
Results: P. acnes IE is rare, though its prevalence is probably underestimated. It is most likely to affect men (71%), and affects all ages (children 4/31 cases). An entry point, probably cutaneous, is rarely confirmed. P. acnes IE often develops on valve prosthesis (42%), and embolisms are common (61%). The infective site is usually aortic (55%). The often-subtle symptoms and slow growth of the organism in vitro complicate the diagnosis, which is often made at a late stage, when valvular and peri-valvular destruction has become major. Despite the high sensitivity of P. acnes to most antimicrobials, a surgical intervention is very often needed (81%). The mortality is relatively high (15% to 27%). Examination of pathologic specimens by polymerase chain reaction increases the sensitivity and speed of its detection. The identification of P. acnes in a biologic specimen, valvular tissue in particular, requires a thorough knowledge of the clinical context before concluding to contamination, and mandates close surveillance of the patient. P. acnes can be the cause of IE long before it has been detected.