National Laboratory Surveillance of Invasive Streptococcal Disease in Canada - Annual Summary 2016

Executive Summary

Streptococcus pneumoniae: 2,906 isolates causing invasive pneumococcal disease (IPD) were characterized in 2016.

In 2015 (most recent data available at time of publication), incidence of IPD declined in children under <1 year of age to 14.5 cases per 100,000 population; and in seniors ≥60 years to 20.3 cases per 100,000 population. The overall crude incidence rate has remained stable averaging 9.0 cases per 100,000 population since 2013.

PCV7 serotypes increased in 2016 accounting for 11% of IPD. This increase can be attributed primarily to an increase of serotype 4 isolations among adults in Western Canada.

PCV13 serotypes accounted for 20% of overall IPD, continuing an overall decline from 36% in 2012. However, a troubling increase of PCV13 serotypes in children <2 years of age has been driven by the resurgence of serotypes 3 and 19A in this age group since 2014. Continued declines of PCV7 and PCV13 serotypes in seniors ≥65 years of age, as well as lower case rates in this age group, indicate indirect reduction of disease most likely through herd immunity effects.

Overall levels of PPV23 and non-vaccine serotypes (NVT) have remained relatively unchanged in 2016 at 39% and 31%, respectively.

Predominant serotypes in 2016 were serotype 3 (9%), 22F (9%), 4 (7%), 19A (6%) and 8 (5%). 15B/C was the most prevalent serotype in <2 year olds accounting for 16% and in 2–4 year olds with 13%. An increase of serotype 4 in adults was associated with Western regions; 23B was predominant in 2–14 year olds, and 15A was associated with the 2–4 year old age group in 2016.

Antimicrobial susceptibility: Testing of 1,114 isolates indicated levels of resistance were again relatively stable during 2016 with the following resistance rates: clarithromycin (22%), penicillin (12%), doxycycline (9%), clindamycin (4%), trimethoprim/sulfamethoxazole (6%), meropenem (0.7%), and imipenem (0.3%). Serotypes 6A, 6C, 19A, 15A, 23A and 35B generally had the highest rates of antimicrobial resistance. Multi-drug resistance decreased slightly from 7% in 2015 to 6% in 2016. The highest rates of multi-drug resistance were seen in serotypes 15A (78%) and 19A (15%).

S. pyogenes (Group A Streptococcus): 1,792 isolates causing invasive disease were characterized for emm type.

Overall incidence of invasive disease has increased from 4.0 to 5.3 cases per 100,000 population from 2009 to 2015.

Despite a dramatic decline since 2012, emm1 continues to be most predominant among all combined age groups (15%). Regional increases of emm89 in the East (13%), emm74 in Central (9%), and emm81 in the West (17%) have been noted.

Antimicrobial susceptibility: Antimicrobial resistance of S. pyogenes is relatively low, however small increases were seen in 2016 with chloramphenicol non-susceptibility at 4%, erythromycin resistance at 9%; and clindamycin resistance at 4%.

S. agalactiae (Group B Streptococcus): There were 228 invasive Group B Streptococcus submitted to NML during 2016, of which 9 isolates were from early onset cases (infants ≤7 days old) and 11 were from late onset cases (infants 8 – 31 days old). Incidence of invasive disease among infants ≤31 days has increased from 27.6 to 33.8 cases per 100,000 population from 2009 to 2015.

Serotypes Ia (24%), III (19%) and IV (18%) were most predominant.

Antimicrobial susceptibility: Resistance to erythromycin increased to 57% while clindamycin resistance increased to 35%.

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