Abstract
BACKGROUND: The objective of this study was to characterize longitudinal colonization with Streptococcus pneumoniae during the first year of life within a community newborn infant cohort, and assess the relationship between antibiotic exposure and colonization with antibiotic-resistant organisms. METHODS: During April 2013-February 2014, 326 infants were enrolled from an urban academic hospital well-baby nursery. At ages 4, 8, and 12 months, we collected antibiotic data, other exposure data, and nasopharyngeal cultures for pneumococcal isolation. RESULTS: Follow-up visits were completed for 211, 158, and 144 infants at ages 4, 8, and 12 months, respectively. By 12 months, 33% of infants attending the visits had ever been exposed to antibiotics, 67% if exposures to maternal antibiotics at birth are included. Pneumococci were isolated at 38/839 (4.5%) visits from 38 infants, including one 13-valent conjugate vaccine (PCV13) serotype (6A). There were 1 (0.3%), 15 (7%), 7 (4%), and 15 (10%) infants who were colonized at 0-, 4-, 8-, and 12-month visits, respectively. By age 12 months, at least 35 (11%) infants had ever been colonized. Sixteen isolates (42%) exhibited nonsusceptibility to at least 1 antibiotic. Infants with recent antibiotic exposure were not more likely to be colonized or to harbor nonsusceptible organisms. CONCLUSIONS: Within a hospital birth cohort followed in the community, pneumococcal colonization and related antibiotic resistance were lower than previously reported, likely associated with PCV13 use. Antibiotic exposure was not associated with subsequent colonization with resistant isolates. The influence of other environmental factors needs further study.