Propionibacterium acnes infections after cranial neurosurgery

Propionibacterium acnes (P. acnes) is a relatively avirulent organism that is part of the normal skin flora. Most patient isolates are considered contaminants but, in a small subset of patients, particularly in the post-neurosurgery setting, the organism can cause significant infections. We reviewed our experience with the occurrence and management of P. acnes infections after cranial neurosurgical procedures over a five-year period.

Patients with positive cultures for P. acnes between 1996 and 2001 were identified by review of the Saskatoon Health Region microbiology laboratory database. Of the 141 positive cultures, a review of hospital records identified six patients with P. acnes infections after neurosurgical procedures. A review of the literature related to P. acnes associated CNS infections was conducted.

All patients had undergone a craniotomy or burrhole placement, and one patient had received prior radiotherapy. There were no P. acnes-related ventriculoperitoneal shunt infections. All patients presented with scalp swelling and three had purulent discharge. Symptoms occurred more than two months after the initial surgery in five of six patients, while one patient developed symptoms three years post-operatively. Management for all patients included removal of the craniotomy flap and treatment with parenteral antibiotics, followed in most cases by oral antibiotics. A good response without relapse of infection was seen in five patients; one patient had recurrent infection after cranioplasty.

P. acnes is a rare but important cause of infection after craniotomy. Wound debridement, removal of the bone flap and adequate antibiotic coverage result in cure in the majority of patients.