2714. Streptococcus pneumoniae Nasopharyngeal Carriage in Canadian Adults Hospitalized with Community-Acquired Pneumonia from 2010 to 2017

BACKGROUND: Streptococcus pneumoniae can colonizes the human nasopharynx, and can cause life-threatening infections like community-acquired pneumonia (CAP) and invasive pneumococcal diseases (IPD). In Canada, the 13-valent conjugate vaccine (PCV13) was introduced in childhood immunization since 2010, with hopes that it would not only protect the vaccinated, but also confer indirect protection to adults through herd immunity. Given data on S. pneumoniae nasopharyngeal (NP) carriage in adults is scarce, this study reports on S. pneumoniae-positivity and serotype distribution in adult carriage from years 2010 to 2017. METHODS: Active surveillance was performed in adults hospitalized with for CAP or IPD from December 2010 to 2017. For assessment of S. pneumoniae carriage, NP swabs were tested using lytA and cpsA real-time PCR. S. pneumoniae-positive NPs were subjected to serotyping using conventional and real-time multiplex PCRs. RESULTS: Overall, 6472 NP swabs were tested, and Spn was identified in 366 (5.7%). Of the 366 S. pneumoniae-positive NP swabs, a serotype was assigned in 355 (97.0%). From years 2010 to 2017, the proportion of S. pneumoniae-positive NP swabs declined from 8.9% to 4.3%. This was also reflected in the proportion of serotypeable results attributed to PCV13 serotypes, which also declined from 76.9% to 42.2%. The decline was primarily attributed to PCV13 serotypes 7F and 19A. PCV13 serotype 3 remained predominant throughout the study, as did non-PCV13 serotypes like 22F, 33F, and 11A. On the other hand, a proportional rise over time was noted for non-vaccine serotypes (from 15.4% to 31.1%). This was primarily attributed to serotypes 23A, 15A, and 35B. CONCLUSION: Monitoring serotype trends is important to assess the impact of pneumococcal vaccines. While herd immunity from PCV13 childhood immunization was anticipated, few studies have assessed its impact on adult carriage. This study described Spn serotype distribution in adults over years 2010 to 2017, demonstrating not only a reduction of PCV13 serotypes over time, but a proportional rise in non-vaccine serotypes. These emerging serotypes may represent the emergence of serotype replacement. Ongoing serotype surveillance will be needed to compare S. pneumoniae carriage to serotypes associated with pneumococcal CAP and IPD. DISCLOSURES: All authors: No reported disclosures.