title: Quantification of the antibody response to Propionibacterium acnes in a patient with prosthetic valve endocarditis: - a case report.
abstract: BACKGROUND
  The isolation of Propionibacterium acnes in blood cultures is often considered a contaminant. On rare occasions, P. acnes can cause severe infections, including endocarditis and intravascular prosthesis-associated infections. To evaluate the discrimination between a contaminant and a clinically relevant infection we used an Ouchterlony test system to quantify the antibody response to P. acnes in a patient with a proven P. acnes endocarditis.
  
  
  METHODS
  We report on a 64-year-old Caucasian man who developed P. acnes endocarditis four years following a composite valve-graft conduit replacement of the aortic root. Bacterial growth in blood cultures was detected after an incubation period of 6 days. However, the antibody titer to P. acnes was 1:8 at the time of diagnosis and declined slowly thereafter over 2½ years. The patient's response to the antibiotic treatment was excellent, and no surgical re-intervention was necessary.
  
  
  CONCLUSIONS
  The working hypothesis of infective endocarditis can be substantiated by serologic testing, which, if positive, provides one additional minor criterion. Moreover, quantification of the antibody response to P. acnes, though not specific, may assist in the differentiation between contaminants and an infection. This quantification may have implications for the patient management, e.g. indication for and choice of the antibiotic therapy.
authors.affiliation: Department of Medicine, Limmattal Hospital, Urdorferstrasse 100, CH-8952, Schlieren, Switzerland. thomas.herren@spital-limmattal.ch.
authors.forename: T
authors.initials: T
authors.lastname: Herren
authors.affiliation: Department of Surgery, Kantonsspital, Im Ergel 1, CH-5404, Baden, Switzerland.
authors.forename: M A
authors.initials: MA
authors.lastname: Middendorp
authors.affiliation: Microbiological Laboratory, Limmattal Hospital, Urdorferstrasse 100, CH-8952, Schlieren, Switzerland.
authors.forename: R
authors.initials: R
authors.lastname: Zbinden
mesh_terms: D000900:Anti-Bacterial Agents / Q000627:therapeutic use; D000907:Antibodies, Bacterial / Q000097:blood*; D001021:Aortic Valve; D004452:Echocardiography; D004697:Endocarditis, Bacterial / Q000175:diagnosis* / Q000188:drug therapy / Q000382:microbiology; D016908:Gram-Positive Bacterial Infections / Q000175:diagnosis* / Q000188:drug therapy / Q000382:microbiology; D006352:Heart Ventricles / Q000000981:diagnostic imaging; D006801:Humans; D008297:Male; D008875:Middle Aged; D011425:Propionibacterium acnes / Q000235:genetics / Q000276:immunology* / Q000302:isolation & purification; D016459:Prosthesis-Related Infections / Q000188:drug therapy / Q000382:microbiology
chemical_list: D000900:Anti-Bacterial Agents; D000907:Antibodies, Bacterial
keywords: Bacteremia; Contamination; Infective endocarditis; Propionibacterium acnes; Prosthetic heart valve; Serologic tests