Clinical and Epidemiologic Review of Capnocytophaga Spp. Infections Identified at a Public Health Reference Laboratory-California, 2005-2021

Introduction: Capnocytophaga is a genus of bacteria that are commensal to the oral microbiome of humans and some animals. Some Capnocytophaga species are found in the human oral cavity and rarely cause disease in people; the species found in animals are zoönotic and can be transmitted to people via saliva. This study describes the clinical and epidemiologic features of patients from whom Capnocytophaga spp. were isolated from blood and other clinical specimens at the California state Microbial Diseases Laboratory.

Methods: Clinical information was obtained from laboratory submission forms and any accompanying medical records and/or from matching records in statewide hospital discharge and emergency department databases.

Results: During the 17-year study period (2005-2021), Capnocytophaga spp. were isolated in 48 specimens from 47 patients. Capnocytophaga canimorsus, which is a zoönotic species, represented 85% of the Capnocytophaga spp. identified to the species level. The median age was 67 years (range: 30-88 years) for the 42 patients infected with a zoönotic species of Capnocytophaga and 36 years (range: 12-65 years) for the four patients infected with a non-zoönotic species. Twenty-five (60%) patients with zoönotic species infections were male, compared to two (50%) patients with non-zoönotic species infections. Capnocytophaga spp. were most frequently isolated from blood (88%), and the most common case presentation was sepsis (45%). A dog or cat bite prior to diagnosis was reported for 14% of patients infected with a zoönotic species of Capnocytophaga. Records for 45% of patients indicated at least one pre-existing health condition associated with depressed immune function.

Conclusions: This study documented that Capnocytophaga spp. can cause rare, severe, invasive disease in mostly older or immunocompromised persons, often without documentation of a dog or cat bite. Providers are encouraged to consider Capnocytophaga spp. infection in immunocompromised pet owners presenting with sepsis, even in the absence of a known animal bite.