Invasive pneumococcal disease surveillance in Canada, 2020

Abstract

Background: Invasive pneumococcal disease (IPD), which is caused by Streptococcus pneumoniae, has been a nationally notifiable disease in Canada since 2000. The use of conjugate vaccines has markedly decreased the incidence of IPD in Canada; however, the distribution of serotypes has shifted in favour of non-vaccine types. This report summarizes the demographics, serotypes and antimicrobial resistance of IPD infections in Canada in 2020.

Methods: The Public Health Agency of Canada's National Microbiology Laboratory (Winnipeg, Manitoba) collaborates with provincial and territorial public health laboratories to conduct national surveillance of IPD. A total of 2,108 IPD isolates were reported in 2020. Serotyping was performed by Quellung reaction and antimicrobial susceptibilities were determined in collaboration with the University of Manitoba/Canadian Antimicrobial Resistance Alliance. Population-based IPD incidence rates were obtained through the Canadian Notifiable Disease Surveillance System.

Results: Overall incidence of IPD in Canada decreased significantly from 11.5 (95% confidence interval [CI]: 10.1-13.1) to 6.0 (95% CI: 5.0-7.2), and from 10.0 (95% CI: 9.7-10.3) to 5.9 (95% CI: 5.7-6.2) cases per 100,000 from 2019 to 2020; in those younger than five years and those five years and older, respectively. The most common serotypes overall were 4 (11.2%, n=237), 3 (10.9%, n=229) and 8 (7.2%, n=151). From 2016 to 2020, serotypes with increasing trends (p<0.05) included 4 (6.4%-11.2%), 3 (9.5%-10.9%), 8 (5.2%-7.2%) and 12F (3.6%-5.7%). The overall prevalence of PCV13 serotypes increased over the same period (30.3%-34.9%, p<0.05). Antimicrobial resistance rates in 2020 included 23.0% clarithromycin and 9.9% penicillin (IV meningitis breakpoints). Multidrug-resistant IPD has significantly increased since 2016 (4.2%-9.5%, p<0.05).

Conclusion: Though the incidence of IPD decreased in 2020 in comparison to previous years across all age groups, disease due to PCV13 serotypes 3 and 4, as well as non-PCV13 serotypes such as 8 and 12F, increased in prevalence. Continued surveillance of IPD is imperative to monitor shifts in serotype distribution and antimicrobial resistance.

Keywords: Canada; IPD; PCV13; Streptococcus pneumoniae; antimicrobial resistance; invasive pneumococcal disease; pneumococcus; serotype; surveillance.

Figure 1

Annual incidence of invasive pneumococcal disease cases per 100,000 population in Canada by age group, 2010–2020

Figure 2

Invasive Streptococcus pneumoniae serotype prevalence trends by age, 2016–2020^a,b All combined age groups Younger than five years of age 65 years of age and older ^a For serotypes with an overall (2016–2020) N≥30: up or down arrows indicate statistically significant trends toward increasing or decreasing prevalence for the 2016–2020 timespan, using the chi-squared test for trend. Serotypes with no arrow either did not demonstrate a statistically significant trend or did not have an overall N≥30. Trends for more detailed age groups can be found in the Supplemental material as Figures S5 to S9 ^b Serotypes 15B and 15C were grouped together as 15B/C because of reported reversible switching between them in vivo during infection, making it difficult to precisely differentiate between the two types ( ((16,17))) ^c Component of PCV13 ^d Component of PCV15 ^e Component of PCV20 ^f Component of PPV23 ^g Number of isolates for 2016, 2017, 2018, 2019 and 2020 respectively

Figure 3

Invasive Streptococcus pneumoniae serotype trends by vaccine and age^a, 2016–2020 A) Younger than five years of age B) 65 years of age and older Abbreviation: NVT, non-vaccine serotype ^a Vaccine serotypes include PCV13 (1, 3, 4, 5, 6A, 6B, 7F, 9V, 14, 19A, 19F, 18C, 23F); PCV15 (all PCV13 plus 22F and 33F); PCV20 (all PCV15 plus 8, 10A, 11A, 12F, 15B/C) and PPV23 (PCV20 serotypes except 6A, plus 2, 9N, 17F, 20); NVT=all serotypes not included in PCV13, PCV15, PCV20 and PPV23. Serotypes 15B and 15C were grouped together as 15B/C because of reported reversible switching between them in vivo during infection, making it difficult to precisely differentiate between the two types ( ((16,17))). Trends for more detailed age groups can be found in the Supplemental material as Figures S17 to S21 and Tables S2 to S7

Figure 4

Annual trend of multidrug resistance of invasive Streptococcus pneumoniae, 2016–2020 ^a Antimicrobial classes include: β-lactams (amoxicillin/clavulanic acid, penicillin using meningitis breakpoints, ceftriaxone using meningitis breakpoints, imipenem and meropenem); macrolides (clarithromycin); fluoroquinolones (levofloxacin); tetracyclines (doxycycline); folate pathway inhibitors (trimethoprim-sulfamethoxazole); phenicols (chloramphenicol); lincosamides (clindamycin); oxazolidinones (linezolid)