A Rare Case of a Brain Abscess With a History of Penicillin Allergy

The administration of β-lactam antibiotics is the standard treatment for brain abscesses. However, there are no detailed case reports of brain abscesses with a history of allergy to β-lactam antibiotics. Here, we present the case of a patient with a penicillin allergy who underwent successful treatment for a brain abscess without the recurrence of anaphylaxis symptoms. A 91-year-old man was admitted with a brain abscess. β-Lactam antibiotics were not considered to be suitable because the patient had previously developed anaphylaxis symptoms to penicillin antibiotics. Due to poor oral hygiene, anaerobic bacteria were suspected as the underlying cause of the brain abscess. Intravenous metronidazole (MNZ) therapy was initiated after intracerebral drainage. <i>Fusobacterium necrophorum</i> was isolated from a culture of pus obtained via drainage. We concluded that the abscess was caused solely by <i>F. necrophorum</i> because aerobic cultures of the abscess were completely negative, whereas <i>F. necrophorum</i> was isolated only under anaerobic conditions. Following 45 days of MNZ therapy, the patient was discharged without the recurrence of anaphylaxis. The learning point of this case is that physicians must confirm patient histories of antibiotic allergies and adjust treatment based on the information collected, particularly for patients with a history of penicillin allergy.