Propionibacterium acnes is a Gram-positive microaerophilic bacterium and part of the human skin flora. The ability of P. acnes to cause infections has been recognized, particularly in the presence of hardware. We aimed to define the frequency of P. acnes infections, with a focus on aortic graft infection.
We used microbiology laboratory records at the Minneapolis Veterans Affairs Health Care System to identify all P. acnes cultures from January 2007 to January 2017. We retrospectively reviewed all adult (≥18 years) patient’s medical records to identify associated infectious syndromes. Case definitions by the management of Aortic Graft Infection Collaboration were used to classify aortic graft infection cases.
We identified 328 positive P. acnes cultures during the study period. P. acnes was classified as a pathogen in 48 (15%), a pathogen of undetermined significance in 70 (21%), and a contaminant in 210 (64%) cases. We identified 3 cases aortic graft infection which accounted for (2.5%) of infections caused by P. acnes. Median age (range) at presentation was 74 years (67-83). Symptoms included pain (n = 3), fever (n = 2), and altered mental status (n = 1). None were hypotensive. All patients had at least one revision for endoleak prior to presentation. Median time from symptom onset to diagnosis was 120 days (78-140). Microbiological diagnosis was obtained by blood cultures, percutaneous peri-graft tissue aspiration, and operative culture in each patient, respectively. Infection was complicated by metastatic abscess in one patient. All cultures grew on day 7. All patients were treated with IV ceftriaxone, and two were transitioned to life-long oral suppressive antibiotic therapy. Two patients had complete removal of infected material. No relapse was documented and survival was 100% at one year follow up.
Aortic graft infection is an uncommon subset of infections caused P. acnes. Clinical course is indolent and diagnosis is delayed due to non-specific clinical presentation. In contrast to endovascular graft infection caused by other organisms, mortality is low when treated with appropriate antibiotic therapy and removal of infected material. The current laboratory practice of holding blood cultures for 5 days may need to be altered when P. acnes is a potential cause of infection.
A. El Rafei,