Pneumococcal carriage, density, and co-colonization dynamics: a longitudinal study in Indonesian infants.

OBJECTIVES: Nasopharyngeal carriage of Streptococcus pneumoniae underpins disease development and transmission. We examined pneumococcal carriage dynamics, including density and multiple serotype carriage, in Indonesian infants during the first year of life. METHODS: 200 healthy infants were enrolled at 2 months of age, with 8 nasopharyngeal swabs collected from enrolment until 12 months of age. Pneumococci were detected using quantitative PCR and serotyped by microarray. Regression models assessed factors influencing pneumococcal carriage and density. RESULTS: 85% of infants carried pneumococci at least once during the study. The median age of first acquisition was 129 days (IQR 41, 216). The median duration of carriage was longer for the first pneumococcal acquisition compared with subsequent acquisitions (151 days vs 95 days, p < 0.0001). Of 166 infants who carried pneumococci during the study, the majority (63.9%) carried a single pneumococcal serotype at a time. Pneumococcal carriage density was higher when upper respiratory tract infection symptoms were present, lower during antibiotic usage, decreased with age, and tended to decrease over time during a carriage episode. CONCLUSIONS: The majority of Indonesian infants carry pneumococcus at least once during the first year of life. Pneumococcal carriage is a dynamic process, with pneumococcal density varying during a carriage episode.