2004 Abstract : CS 4

Authors: CE Marculescu, EF Berbari, JM Steckelberg, AD Hanssen, and DR Osmon

Title: Medical Therapy and Outcome of Prosthetic Joint Infections (PJI) Due to Propionibacterium acnes

Addresses: Mayo Clinic Rochester, MN; 200 First Street, SW, Rochester, MN 55905.

Purpose: To analyze the outcome of prosthetic joint infection (PJI) due to Propionibacterium acne .

Methods: Records of all cases of THA and TKA infections due to P. acnes, using a strict case definition, diagnosed during 1/1995-12/1999 were reviewed. Kaplan-Meier survival method was used to determine the cumulative probability of success.

Results: 22/509 (4.3%) of PJI episodes were caused by anaerobes. P. acnes caused 12/22 (55%) of PJI due to anaerobes. The median age of the cohort (12 patients) was 63 years (range 41-77). 75% of patients were males. 58% (7/12) of PJI episodes involved a THA. Pain and/or loosening were the main symptoms, occurring in 11/12 (91%) of patients with P. acnes PJI. One patient had acute onset of cellulitis. No patient had a sinus tract present. The median duration of symptoms was 84 days (range:1-168). Five patients had positive intraoperative cultures (PIOC) with P. acnes following one-stage revision arthroplasty. One patient had one-stage exchange for a known THA PJI due to P. acnes. A two-stage exchange was done in 3 patients, two involving a TKA and one a THA. The median time from resection to reimplantation was 42 days (range: 42-92). Antibiotic-impregnated spacers were used in 2/3 patients treated with two-stage exchange. Arthrodesis was performed in another patient, and girdlestone in one patient with P. acnes PJI, respectively. One patient received medical therapy only, and had no surgical procedure performed. Antibiotic- impregnated cement with vancomycin/tobramycin or vancomycin alone was used in 50% of PJI episodes. In vitro susceptibility data for P. acnes were performed in 8/12 (66.6%) of patients. All 8 P. acnes isolates for which susceptibility data were available were susceptible to PCN (MIC <0.5), ceftriaxone (MIC<0.5), clindamycin (MIC<0.5) and were uniformly resistant to metronidazole. Intravenous antimicrobial therapy was administered in 8/12 patients (66%) for a median of 42 days (range: 28-60). b-lactams antibiotics were used for all patients. Cefazolin was used in 5 patients and ceftriaxone in 3 patients. Chronic oral antimicrobial suppression was used in 6 patients (50%), for a median length of 218 days (14-394). Three patients received oral first generation cephalosporins, two received penicillins, and one patient received trovafloxacin. Two patients with PIOC due to P. acnes following revision arthroplasty received no antimicrobial therapy at all. No side effects of antimicrobial therapy were seen in this cohort. Three treatment failures occurred : one was reinfection with a different microorganism in a patient with a one-stage exchange and PIOC. The other 2 were indeterminate clinical failures. One of these occurred in a patient who received oral antimicrobial suppression only, and the other one in a patient with a THA PJI treated with a two-stage exchange. The 2-year cumulative probability of success for the cohort was 81% (95%CI: 54-94%).

Discussion: P. acnes is the most common anaerobic organism that can cause PJI.. P. acnes is often discovered incidentally following one-stage revision arthroplasty as PIOC. P. acnes is susceptible to b-lactam antibiotics, including cephalosporins, making cefazolin or ceftriaxone a convenient and attractive option. The outcome of PJI due to P. acnes is very good utilizing different surgical and medical strategies, including chronic oral suppression.