Changing trends in β-hemolytic streptococcal bacteremia in Manitoba, Canada: 2007-2012

European surveillance studies have reported an increasing incidence of β-hemolytic group G streptococcal bacteremia, but no studies have evaluated trends in β-hemolytic streptococcal bacteremia in North America.

We reviewed bacteremic episodes and positive throat swab cultures from two tertiary care centers in Manitoba, Canada, from January 2007 to December 2012.

During the study period, 19 864 bacteremic episodes, and 9948 positive throat swabs were identified. There were 1025 (5.16%) bacteremic episodes attributable to β-hemolytic streptococci: 425 (2.03%), 339 (1.71%), 62 (0.31%), and 199 (0.95%) to β-hemolytic groups A, B, C, and G streptococci, respectively. From 2007 to 2012, there were significant increases in the proportion of bacteremia attributable to β-hemolytic streptococci in general (6.32% vs. 4.02%; p<0.0001; linear trend test, p<0.0001), and to groups G (1.49% vs. 0.43%; p<0.0001; linear trend test, p<0.0001) and C (0.58% vs. 0.13%; p=0.0068; linear trend test, p=0.0105) β-hemolytic streptococci in particular. Bacteremia attributable to groups A and B β-hemolytic streptococci and Streptococcus pneumoniae were unchanged. There were no changes in the distribution of β-hemolytic streptococcal groups among throat swabs.

Bacteremia attributable to β-hemolytic groups G and C streptococci increased in Manitoba, Canada. Further study of the factors underlying these changes is required.