Cutibacterium acnes Osteitis of the Cranial Bone Flap Following Craniotomy: A Case Report.

BACKGROUND: Cutibacterium acnes is a slow-growing anaerobic gram-positive bacillus increasingly recognized as a cause of delayed, indolent post-surgical infections, particularly in the context of implants or bone flaps. Diagnosis is often challenging due to its slow growth and tendency to be dismissed as a contaminant. CASE PRESENTATION: We describe a case of C. acnes osteitis involving a cranial bone flap in a patient who underwent craniotomy and tumour decompression for a high-grade glioma. The postoperative course was initially uneventful; however, several weeks later the patient developed low-grade pyrexia and purulent wound discharge. Anaerobic culture of bone material yielded pure growth of C. acnes identified by MALDI-TOF MS (VITEK® MS). Antimicrobial susceptibility testing demonstrated resistance to penicillin and metronidazole, with susceptibility to multiple other agents. The patient responded favourably to targeted antimicrobial therapy with no recurrence on follow-up. CONCLUSION: C. acnes represents an important but under-recognised cause of delayed post-craniotomy infection. Prolonged anaerobic incubation, modern proteomic identification techniques, and careful clinicomicrobiological correlation are essential for accurate diagnosis. Combined surgical and antimicrobial management results in excellent outcomes.