Uncommon Cause of Meningitis: Lactobacillus mucosae Meningitis in a Patient With Recurrent CSF Leak Post-craniotomy

Meningitis is a serious infection with potentially life-threatening consequences if not promptly treated. Common bacterial pathogens include <i>Streptococcus pneumoniae</i>, <i>Neisseria meningitidis</i>, and <i>Haemophilus influenzae</i>. However, in rare instances, less common organisms can cause meningitis, particularly in individuals with predisposing conditions, such as a cerebrospinal fluid (CSF) leak. Here we present the case of a 63-year-old male with a history of craniotomy and CSF leaks who developed meningitis due to <i>Lactobacillus mucosae</i>. He presented with severe headaches, photophobia, diaphoresis, nasal discharge, and nuchal rigidity. He was found to have a CSF leak confirmed by positive beta-2 transferrin. CSF analysis revealed elevated WBCs, elevated protein, and normal glucose. Blood cultures grew <i>Lactobacillus mucosae</i>. MRI brain revealed a depression of the cribriform plate with cortical discontinuity and a small encephalocele, likely the source. The patient was successfully treated with a total of 10 days of intravenous antibiotics and steroids and was transferred to another facility for neurosurgical repair. No recurrence was reported 8 months post-treatment during a subsequent hospitalization for an unrelated issue. Lactobacillus meningitis is rare in the literature; to our knowledge, this is the first case involving <i>Lactobacillus mucosae</i>. This case illustrates the importance of considering atypical pathogens in patients with risk factors such as cranial surgery and CSF leaks who present with signs of meningitis. The presence of an encephalocele and cortical discontinuity further complicated the clinical picture, requiring a careful and coordinated approach to management.