INTRODUCTION: Capnocytophaga canimorsus infections are associated with dog 
bites, especially in asplenic or immunocompromised patients, and typically 
manifest as sepsis and/or bacteremia. Meningitis has been rarely described, and 
its diagnosis may be delayed due to poor or slow growth using traditional 
culture techniques. We provide our experience using polymerase chain reaction 
(PCR) to establish the diagnosis and perform a comprehensive review of C. 
canimorsus meningitis cases to provide summary data on the clinical 
manifestations, diagnosis, and outcomes of this unusual infection.
METHODS: A systematic review of the peer-reviewed English literature (PubMed, 
Embase, Ovid Medline) from January 1966 to March 2018 was conducted to identify 
cases of C. canimorsus meningitis. Data collected included demographics, risk 
factors, cerebrospinal fluid (CSF) findings, PCR results, treatments, and 
outcomes. Descriptive statistics are presented as numbers (percentages) and 
medians (ranges).
RESULTS: A total of 37 patients were reviewed with a median age of 63 years 
(12 days to 83 years) with a male predominance (76%). A relatively low 
proportion had an immunocompromised state (16% splenectomy and 5% steroid use); 
the most common risk factor was alcoholism (19%). Fifty-nine percent reported a 
dog bite (all within ≤ 14 days prior to presentation), while 22% reported a 
non-bite dog exposure, 3% reported cat bite, and 3% reported both dog and cat 
exposures; 11% reported no animal contact. CSF parameters included a median 
white count of 1024 cells/mm3, 81% had neutrophilic predominance, median protein 
of 190 mg/dl, and median glucose CSF/serum ratio 0.23. In 54% of cases, blood 
cultures were positive for C. canimorsus (median, 4 days) and 70% had positive 
CSF cultures (median, 5 days). PCR established the diagnosis in eight (22%) 
cases. Antibiotic therapy was given for a median of 15 days (range, 7 to 
42 days). Prognosis was overall favorable with only one (3%) death reported and 
adverse neurologic and/or physical sequelae in 19% of the survivors.
CONCLUSION: C. canimorsus meningitis is a rare but increasingly important 
clinical entity occurring in patients of all ages, typically after dog exposure. 
While classically considered an infection among immunocompromised patients, most 
cases have occurred in previously healthy, immunocompetent persons. Diagnosis 
may be rapidly established by PCR, and this test should be considered in 
culture-negative cases with associated exposures. Outcome was generally 
favorable after a median antibiotic duration of 15 days.