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Quantification of the antibody response to Propionibacterium acnes in a patient with prosthetic valve endocarditis: -
T Herren1, M A Middendorp2, R Zbinden3
1Department of Medicine, Limmattal Hospital, Urdorferstrasse 100, CH-8952, Schlieren, Switzerland. thomas.herren@spital-limmattal.ch.
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.
Case Presentation:
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.
Conclusion:
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.
Insights
Quantifying antibody response to Propionibacterium acnes (P. acnes) aids in distinguishing true infections from contaminants. This serologic testing can guide P. acnes infection management and antibiotic therapy choices.
Area of Science:
- Infectious Diseases
- Clinical Microbiology
- Immunology
Background:
- Propionibacterium acnes (P. acnes) isolation from blood cultures is frequently dismissed as contamination.
- However, P. acnes can precipitate severe infections like endocarditis and prosthesis-associated infections.
- Differentiating between contaminants and genuine P. acnes infections is clinically significant.
Observation:
- A case of P. acnes endocarditis in a 64-year-old man following aortic root composite valve-graft replacement is presented.
- P. acnes was identified after a 6-day incubation period in blood cultures.
- Antibody titers to P. acnes were quantified using an Ouchterlony test system.
Findings:
- The patient exhibited an initial antibody titer of 1:8, which gradually decreased over 2.5 years.
- The patient responded well to antibiotic treatment, avoiding further surgery.
- Serologic testing, including antibody quantification, can support the diagnosis of infective endocarditis.
Implications:
- Quantifying the antibody response to P. acnes may help differentiate between contaminants and true infections.
- Serologic results can serve as an additional minor criterion for diagnosing infective endocarditis.
- Antibody quantification may influence patient management, including antibiotic selection and treatment duration.
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