Nasopharyngeal carriage of individual Streptococcus pneumoniae serotypes during pediatric pneumonia as a means to estimate serotype disease potential

BACKGROUND: We aimed at estimating pneumococcal serotype-specific disease potential in pediatric community-acquired alveolar pneumonia (CAAP), by comparing nasopharyngeal pneumococcal carriage during disease to carriage in healthy children. METHODS: Pneumococcal nasopharyngeal cultures were obtained from children <5 years old admitted to the emergency room or hospitalized with radiologically diagnosed CAAP and from healthy controls. Disease potential was estimated by calculating serotype-specific odds ratios (OR) of a given serotype to be carried during disease compared with healthy children (after adjustment for age, ethnicity, previous antibiotic therapy, and season). RESULTS: A total of 603 and 1504 isolates were obtained from CAAP and healthy children, respectively. A significant OR >1.0 of a specific serotype being carried during disease (suggesting a higher disease potential) was observed with serotypes (by decreasing rank) 1, 5, 22F, 7F, 14, 9V, and 19A. A significant OR <1.0 of being carried during disease (suggesting a lower disease potential) was observed with serotypes 6A, 6B, 23A, and 35B. Carriage of PCV7 serotypes (grouped) during CAAP was highest in age group 6 to 17 months. PCV10 and PCV13 provided significantly higher coverage for both 6 to 17 and 18 to 35 month age groups. CONCLUSIONS: It is suggested that serotypes 1, 5, 7F, 9V, 14, 19A, and 22F have a higher disease potential for childhood pneumonia than do serotypes 6A, 6B, 23A, and 35B.