National Laboratory Surveillance of Invasive Streptococcal Disease in Canada - Annual Summary 2015

Executive summary

Streptococcus pneumoniae

2,596 isolates causing invasive pneumococcal disease (IPD) were characterized in 2015 representing 79.6% of the 3,211 cases reported to Canadian Notifiable Disease Surveillance System (CNDSS).

Incidence of IPD has declined in children under <1 year of age to 14.5 cases per 100,000 population in 2015, however rates in the older age groups have remained relatively unchanged. The highest incidence rates were observed in adults aged ≥60 years with 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 slightly in 2015 accounting for 4.9% of IPD in 2014 to 7.3% in 2015. Overall levels of PCV13 serotypes have declined from 26.0% to 23.4% from 2014 to 2015, however increases have been seen in the <2 (7.0% to 14%) and 5 - 14 year (26.1% to 40.0%) old age groups. PPV23 and NVT serotypes have remained relatively unchanged in 2015 at 38.6% and 30.7%, respectively.

Predominant serotypes in 2015 were 22F (9.7%), 3 (9.1%), 19A (8.2%), 7F (5.6%) and 8 (5.3%). Serotype 22F increased in the <2 year olds to 13.2% and in the 2-4 year olds to 14.1%, and has declined slightly in older age groups. Serotype 3 has remained relatively unchanged overall at 9.1% of isolates among all combined ages. A small decrease was seen in 2-4 year olds from 9.1% to 7.8% from 2014 to 2015. Serotypes 4, 12F and 20 were associated with Western regions in the adult age groups in 2015.

Antimicrobial susceptibility: Testing of 1,132 isolates indicated levels of resistance were again relatively stable during 2015 with the following resistance rates: clarithromycin (23.1%), penicillin (10.3%), doxycycline (8.6%), clindamycin (5.9%), trimethoprim/sulfamethoxazole (6.1%), meropenem (1.5%), and imipenem (0.5%). Multi-drug resistance to 3 or more classes of antimicrobials was observed in 6.7% of the isolates tested, an increase from 4.9% in 2014. The highest rates of multi-drug resistance were seen in serotypes 15A (72.4%) and 19A (26.7%).

S. pyogenes (Group A Streptococcus)

A total of 1,492 isolates were tested during 2015 representing 78.8% of the 1,893 cases reported to CNDSS. Overall incidence of invasive disease has increased from 4.7 to 5.1 cases per 100,000 population from 2013 to 2014.

Emm1 (18.0%) continues to be most predominant among all combined age groups, followed by emm3 (8.0%), emm12 (8.0%) and emm81 (7.4%).

Antimicrobial susceptibility: Antimicrobial resistance of S. pyogenes is relatively low, however small increases were seen in 2015 with chloramphenicol non-susceptibility at 1.4%, erythromycin resistance at 8.3%; and clindamycin resistance at 3.3%.

S. agalactiae (Group B Streptococcus)

There were 171 invasive Group B Streptococcus submitted to NML during 2015 of which 8 isolates were from early onset cases (infants ≤7 days old) and 4 were from late onset cases (infants 8 - 31 days old). Incidence of invasive disease among infants ≤31 days has increased from 35.4 to 38.4 cases per 100,000 population from 2013 to 2014.

Serotypes V (23.4%), III (18.7%) and Ib (17.0%) were most predominant.

Antimicrobial susceptibility: Resistance to erythromycin declined slightly to 44.7% while clindamycin resistance remained relatively unchanged at 28.2%, and no isolates were chloramphenicol non-susceptible in 2015.

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