Bacterial meningitis and subdural empyema caused by Actinomyces canis in a dog

Actinomyces canis, a Gram-positive facultative anaerobe, was identified as the cause of subdural empyema in a two-year-old labrador retriever. The dog was initially treated for conjunctivitis and a week later presented for progressive neurologic abnormalities. Thoracic radiographs showed pulmonary nodules and MRI of the head was suggestive of right retrobulbar cellulitis and presumably consequential, subdural empyema and meningoencephalitis associated with caudal transtentorial herniation. A craniectomy was performed and the aetiologic diagnosis was confirmed by anaerobic bacterial culture. The dog made a complete recovery, including resolution of pulmonary nodules, with surgical decompression and antibiotic treatment.