Group C and G Streptococci: An Emerging Cause of Endocarditis and Severe Infections in Manitoba, Canada

Background: The incidence of Group C and G streptococcal (GCS and GGS, respectively) bacteremia is on the rise, with rates surpassing invasive Group A Streptococcal (GAS) infection. While GCS and GGS have largely been considered commensal human flora, there have been increasing reports of infectious endocarditis (IE), up to 50% in some series. Despite these trends, IE from GCS and GGS is often under investigated. We present a case series of IE associated with GCS and GGS bacteremia from multiple centers in Manitoba, Canada.

Methods: Individuals with blood culture growth of GCS and GGS from two microbiology laboratories in Manitoba, Canada, between January 2012 to December 2015 were included. Clinical and echocardiographic parameters including demographics, co-morbidities, disease severity, valvular abnormalities, vegetations, and outcomes were collected retrospectively via chart review. Using the modified Duke’s criteria and review of the transthoracic echocardiographic (TTE) studies, IE was suspected or confirmed.

Results: A total of 209 bacteremic events occurred in 198, male predominant (63.6%) patients. The average age was 65 years (SD=18.6). TTE was performed in only 32.5%. Of those, 17.9% had suspected IE (12 cases). Four cases were confirmed by the modified Duke’s criteria. Native valve infection was more common than prosthetic valve and device infection (75.0, 16.7, and 8.3%, respectively). Risk factors for IE included intravenous drug use (33.3%), cardiovascular disease (33.3%), and diabetes mellitus (25.0%). Primary bacteremia occurred in all cases without alternate sources of infection. Metastatic infection was seen in 50%, primarily in the lungs (66.7%), spleen (33.3%), and kidneys (33.3%). One patient underwent valve replacement surgery, and another required pacemaker lead extraction. Admission to an intensive care unit was required in 58.3% and the average length of hospitalization for survivors was 26 days (SD=16.9). Mortality from IE was 16.7% (2 events).

Conclusion: High rates of IE are seen with GCS and GGS bacteremia. Severe disease, complications, and mortality is common. IE from GCS and GGS is likely under diagnosed due to low rates of TTE. All GCS and GGS bacteremic events should prompt investigation for IE.