Invasive pneumococcal disease caused by serotypes 22F and 33F in Canada: the SAVE study 2011-2018

Comparison of PCV10, PCV13, PCV15, PCV20 and PPSV23 vaccine coverage of invasive Streptococcus pneumoniae isolate serotypes in Canada: the SAVE study, 2011-20

BACKGROUND

As pneumococci evolve under vaccine, antimicrobial and other selective pressures, it is important to track isolates covered by established (PCV10, PCV13 and PPSV23) and new (PCV15 and PCV20) vaccine formulations.

OBJECTIVES

To compare invasive pneumococcal disease (IPD) isolates from serotypes covered by PCV10, PCV13, PCV15, PCV20 and PPSV23, collected in Canada from 2011 to 2020, by demographic category and antimicrobial resistance phenotype.

METHODS

IPD isolates from the SAVE study were initially collected by members of the Canadian Public Health Laboratory Network (CPHLN) as part of a collaboration between the Canadian Antimicrobial Resistance Alliance (CARA) and the Public Health Agency of Canada (PHAC). Serotypes were determined by quellung reaction, and antimicrobial susceptibility testing was performed using the CLSI broth microdilution method.

RESULTS

A total of 14 138 invasive isolates were collected from 2011 to 2020, with 30.7% of isolates covered by the PCV13 vaccine, 43.6% of isolates covered by the PCV15 vaccine (including 12.9% non-PCV13 serotypes 22F and 33F), and 62.6% of isolates covered by the PCV20 vaccine (including 19.0% non-PCV15 serotypes 8, 10A, 11A, 12F and 15B/C). Non-PCV20 serotypes 2, 9N, 17F and 20, but not 6A (present in PPSV23) represented 8.8% of all IPD isolates. Higher-valency vaccine formulations covered significantly more isolates by age, sex, region and resistance phenotype including MDR isolates. Coverage of XDR isolates did not significantly differ between vaccine formulations.

CONCLUSIONS

When compared with PCV13 and PCV15, PCV20 covered significantly more IPD isolates stratified by patient age, region, sex, individual antimicrobial resistance phenotypes and MDR phenotype.

Genomic investigation of the most common Streptococcus pneumoniae serotypes causing invasive infections in Canada: the SAVE study, 2011-2020

OBJECTIVES

To investigate the lineages and genomic antimicrobial resistance (AMR) determinants of the 10 most common pneumococcal serotypes identified in Canada during the five most recent years of the SAVE study, in the context of the 10-year post-PCV13 period in Canada.

METHODS

The 10 most common invasive Streptococcus pneumoniae serotypes collected by the SAVE study from 2016 to 2020 were 3, 22F, 9N, 8, 4, 12F, 19A, 33F, 23A and 15A. A random sample comprising ∼5% of each of these serotypes collected during each year of the full SAVE study (2011-2020) were selected for whole-genome sequencing (WGS) using the Illumina NextSeq platform. Phylogenomic analysis was performed using the SNVPhyl pipeline. WGS data were used to identify virulence genes of interest, sequence types, global pneumococcal sequence clusters (GPSC) and AMR determinants.

RESULTS

Of the 10 serotypes analysed in this study, six increased significantly in prevalence from 2011 to 2020: 3, 4, 8, 9N, 23A and 33F (P ≤ 0.0201). Serotypes 12F and 15A remained stable in prevalence over time, while serotype 19A decreased in prevalence (P < 0.0001). The investigated serotypes represented four of the most prevalent international lineages causing non-vaccine serotype pneumococcal disease in the PCV13 era: GPSC3 (serotypes 8/33F), GPSC19 (22F), GPSC5 (23A) and GPSC26 (12F). Of these lineages, GPSC5 isolates were found to consistently possess the most AMR determinants. Commonly collected vaccine serotypes 3 and 4 were associated with GPSC12 and GPSC27, respectively. However, a more recently collected lineage of serotype 4 (GPSC192) was highly clonal and possessed AMR determinants.

CONCLUSIONS

Continued genomic surveillance of S. pneumoniae in Canada is essential to monitor for the appearance of new and evolving lineages, including antimicrobial-resistant GPSC5 and GPSC162.

Streptococcus pneumoniae serotyping and antimicrobial susceptibility: assessment for vaccine efficacy in Canada after the introduction of PCV13

BACKGROUND

Streptococcus pneumoniae continues to be an important bacterial pathogen associated with invasive (e.g. bacteraemia, meningitis) and non-invasive (e.g. community-acquired respiratory tract) infections worldwide. Surveillance studies conducted nationally and globally assist in determining trends over geographical areas and allow comparisons between countries.

OBJECTIVES

To characterize invasive isolates of S. pneumoniae in terms of their serotype, antimicrobial resistance, genotype and virulence and to use the serotype data to determine the level of coverage by different generations of pneumococcal vaccines.

METHODS

SAVE (Streptococcus pneumoniae Serotyping and Antimicrobial Susceptibility: Assessment for Vaccine Efficacy in Canada) is an ongoing, annual, national collaborative study between the Canadian Antimicrobial Resistance Alliance (CARE) and the National Microbiology Laboratory, focused on characterizing invasive isolates of S. pneumoniae obtained across Canada. Clinical isolates from normally sterile sites were forwarded by participating hospital public health laboratories to the Public Health Agency of Canada-National Microbiology Laboratory and CARE for centralized phenotypic and genotypic investigation.

RESULTS

The four articles in this Supplement provide a comprehensive examination of the changing patterns of antimicrobial resistance and MDR, serotype distribution, genotypic relatedness and virulence of invasive S. pneumoniae obtained across Canada over a 10 year period (2011-2020).

CONCLUSIONS

The data highlight the evolution of S. pneumoniae under pressure by vaccination and antimicrobial usage, as well as vaccine coverage, allowing both clinicians and researchers nationally and globally to view the current status of invasive pneumococcal infections in Canada.

Non-capsular based immunization approaches to prevent Streptococcus pneumoniae infection

Streptococcus pneumoniae is a Gram-positive bacterium and the leading cause of bacterial pneumonia in children and the elderly worldwide. Currently, two types of licensed vaccines are available to prevent the disease caused by this pathogen: the 23-valent pneumococcal polysaccharide-based vaccine and the 7-, 10, 13, 15 and 20-valent pneumococcal conjugate vaccine. However, these vaccines, composed of the principal capsular polysaccharide of leading serotypes of this bacterium, have some problems, such as high production costs and serotype-dependent effectiveness. These drawbacks have stimulated research initiatives into non-capsular-based vaccines in search of a universal vaccine against S. pneumoniae. In the last decades, several research groups have been developing various new vaccines against this bacterium based on recombinant proteins, live attenuated bacterium, inactivated whole-cell vaccines, and other newer platforms. Here, we review and discuss the status of non-capsular vaccines against S. pneumoniae and the future of these alternatives in a post-pandemic scenario.

Predicting effectiveness of the V114 vaccine against invasive pneumococcal disease in children

BACKGROUND

The potential impact of new pneumococcal conjugate vaccines (PCVs) is assessed by using immune responses to predict their effectiveness against invasive pneumococcal disease (IPD). This analysis predicted the serotype-specific effectiveness against IPD of a new 15-valent PCV (V114) for the serotypes shared with a 13-valent PCV (PCV13), in a US pediatric population given a 3 + 1 dosing regimen.

METHODS

Beginning with the known serotype-specific antibody concentrations after vaccination with placebo, 7-valent PCV (PCV7) and PCV13, reverse cumulative distribution curves were used, along with published serotype-specific vaccine effectiveness of PCV7 and PCV13, to derive a protective antibody concentration (C_p) for each PCV13 serotype in V114. Serotype-specific effectiveness was predicted using the C_p estimates and the respective serotype-specific antibody concentrations of placebo and V114 recipients in recent pediatric clinical trials.

RESULTS

Predicted serotype-specific V114 effectiveness values ranged from 86% to 99% for PCV7 serotypes and from 59% to 97% for (non-PCV7) PCV13 serotypes.

CONCLUSIONS

V114 serotype-specific effectiveness against IPD in a US pediatric population was predicted to be largely comparable to that of PCV7 and PCV13 for shared serotypes, with models suggesting likelihood of high overall benefit gained from increased serotype 3 effectiveness, and additional protection against serotypes 22 F and 33 F.

Whole genome characterization of Streptococcus pneumoniae from respiratory and blood cultures collected from Canadian hospitals before and after PCV-13 implementation in Canada: Focus on serotypes 22F and 33F from CANWARD 2007-2018

The population of pneumococci circulating in Canada is constantly shifting under the pressures of antimicrobial and conjugate vaccine use. A new 15-valent pneumococcal conjugate vaccine (PCV), containing PCV-13 serotypes plus additional serotypes 22F and 33F, is currently undergoing clinical trials. The purpose of this study was to utilize whole genome sequencing to characterize invasive and respiratory Streptococcus pneumoniae isolates collected from Canadian hospitals pre- (2007-2011) and post-PCV-13 implementation (2012-2018) in Canada, particularly serotypes 22F and 33F. Isolates were obtained from the CANWARD 2007 to 2018 study. Overall, 597 S. pneumoniae isolates were sequenced using the Illumina MiSeq platform: 180 (101 respiratory, 79 blood) isolates of serotype 22F, 74 (41 respiratory, 33 blood) isolates of serotype 33F and 343 isolates randomly selected to broadly encompass pneumococci in Canada. Genomes were clustered using PopPUNK v2.0.2 and assigned to a Global Pneumococcal Sequencing Cluster (GPSC) and MLST sequence type (ST), and visualized using Cytoscape v3.8.0. Acquired resistance genes were identified using ResFinder 2.1, and genes with chromosomal mutations conferring resistance were extracted and compared to standard reference genome R6. PopPUNK clustering suggests that a clone of S. pneumoniae serotype 22F/ST433/GPSC19 demonstrating mefA-mediated macrolide resistance is emerging in Canada post-PCV-13 introduction, collected from both invasive and respiratory sources. Similarly, there is evidence to support a post-PCV-13 shift towards macrolide- and trimethoprim/sulfamethoxazole-resistant serotype 33F/ST100/GPSC3, including a cluster associated with invasive isolates. While some lineages containing vaccine serotypes were predominantly identified pre-PCV-13 implementation (serotype 5/GPSC8, serotype 7F/GPSC15), others (serotype 19A/GPSC1 and 4, serotype 3/GPSC12) continue to maintain a significant presence over time despite inclusion in PCV-13. Further genomic surveillance is necessary to determine additional trends over time in these upcoming vaccine serotypes, as well as the overall pneumococcal population in Canada.