Incidence, clinical characteristics, and outcomes of Streptococcus dysgalactiae subspecies equisimilis bacteremia in a tertiary hospital: comparison with S. agalactiae bacteremia

Abstract

Background: Invasive Streptococcus dysgalactiae subspecies equisimilis (SDSE) infections have been reported increasingly. The clinical characteristics and outcomes of patients with SDSE bacteremia have not been adequately evaluated. We reviewed the incidence, clinical characteristics, and outcomes of SDSE bacteremia cases. Methods: We retrospectively enrolled consecutive adult patients with SDSE or S. agalactiae (Group B streptococci, GBS) bacteremia who had been admitted to the Asan Medical Center, a tertiary care hospital in the Republic of Korea, from August 2012 to December 2016. We compared the incidence, seasonality, clinical characteristics, and outcomes of patients with SDSE bacteremia with patients with GBS bacteremia. Results: The incidence of SDSE and GBS bacteremia in admitted patients was 1.28/100,000 and 4.22/100,000 person-days, respectively. A total of 52 SDSE and 151 GBS bacteremia adult cases were finally included for analysis. Most of SDSE bacteremia series were community-onset (SDSE 94.2% vs GBS 83.4%, p = 0.052). Lancefield group G was the most common type among SDSE isolates (43/47, 91.5%). Patients with SDSE bacteremia were older (median 68.0 vs 61.0 years old, p = 0.03) and SDSE bacteremia occurred more common in men than the GBS group (61.5% vs 41.7%, p = 0.01). In both groups, solid tumor (40.4% vs 42.4%, p = 0.80) was the most common underlying disease, and more than half of patients had immunocompromised conditions (51.9% vs 54.3%, p = 0.77). Chronic kidney disease without dialysis was more common in the SDSE group (19.2% vs 5.3%, p < 0.01). The most common clinical syndromes of SDSE bacteremia was cellulitis, which was significantly more common than the GBS group (59.6% vs 29.1%, p < 0.01). SDSE bacteremia cases occurred more frequently in the warm season (June-September) than GBS bacteremia ones (65.4% vs 37.1%, p < 0.01). In-hospital mortality (3.8% vs 10.6%, p = 0.17) and bacteremia-related mortality (3.8% vs 7.9%, p = 0.53) of SDSE bacteremia series were not significantly different from the GBS group. Conclusions: SDSE bacteremia was commonly associated with cellulitis, especially in older and immunocompromised patients during the warm season. However, SDSE bacteremia-related mortality was low even in immunocompromised patients.