title: Impact of experimental human pneumococcal carriage on nasopharyngeal bacterial densities in healthy adults.
abstract: Colonization of the nasopharynx by Streptococcus pneumoniae is a necessary precursor to pneumococcal diseases that result in morbidity and mortality worldwide. The nasopharynx is also host to other bacterial species, including the common pathogens Staphylococcus aureus, Haemophilus influenzae, and Moraxella catarrhalis. To better understand how these bacteria change in relation to pneumococcal colonization, we used species-specific quantitative PCR to examine bacterial densities in 52 subjects 7 days before, and 2, 7, and 14 days after controlled inoculation of healthy human adults with S. pneumoniae serotype 6B. Overall, 33 (63%) of subjects carried S. pneumoniae post-inoculation. The baseline presence and density of S. aureus, H. influenzae, and M. catarrhalis were not statistically associated with likelihood of successful pneumococcal colonization at this study's sample size, although a lower rate of pneumococcal colonization in the presence of S. aureus (7/14) was seen compared to that in the presence of H. influenzae (12/16). Among subjects colonized with pneumococci, the number also carrying either H. influenzae or S. aureus fell during the study and at 14 days post-inoculation, the proportion carrying S. aureus was significantly lower among those who were colonized with S. pneumoniae (p = 0.008) compared to non-colonized subjects. These data on bacterial associations are the first to be reported surrounding experimental human pneumococcal colonization and show that co-colonizing effects are likely subtle rather than absolute.
authors.affiliation: Hubert Department of Global Health, Rollins School of Public Health, Emory University, Atlanta, Georgia, United States of America.
authors.forename: Joshua R
authors.initials: JR
authors.lastname: Shak
authors.affiliation: Laboratory of Pediatric Infectious Diseases, Department of Pediatrics, Radboudumc, Nijmegen, Netherlands.
authors.forename: Amelieke J H
authors.initials: AJ
authors.lastname: Cremers
authors.affiliation: Respiratory Infection Group, Liverpool School of Tropical Medicine, Liverpool, United Kingdom.
authors.forename: Jenna F
authors.initials: JF
authors.lastname: Gritzfeld
authors.affiliation: Laboratory of Pediatric Infectious Diseases, Department of Pediatrics, Radboudumc, Nijmegen, Netherlands.
authors.forename: Marien I
authors.initials: MI
authors.lastname: de Jonge
authors.affiliation: Laboratory of Pediatric Infectious Diseases, Department of Pediatrics, Radboudumc, Nijmegen, Netherlands.
authors.forename: Peter W M
authors.initials: PW
authors.lastname: Hermans
authors.affiliation: Hubert Department of Global Health, Rollins School of Public Health, Emory University, Atlanta, Georgia, United States of America.
authors.forename: Jorge E
authors.initials: JE
authors.lastname: Vidal
authors.affiliation: Hubert Department of Global Health, Rollins School of Public Health, Emory University, Atlanta, Georgia, United States of America.
authors.forename: Keith P
authors.initials: KP
authors.lastname: Klugman
authors.affiliation: Respiratory Infection Group, Liverpool School of Tropical Medicine, Liverpool, United Kingdom.
authors.forename: Stephen B
authors.initials: SB
authors.lastname: Gordon
mesh_terms: D058491:Bacterial Load; D002353:Carrier State; D064368:Healthy Volunteers; D006801:Humans; D009305:Nasopharynx / Q000382:microbiology*; D011008:Pneumococcal Infections / Q000382:microbiology*; D013296:Streptococcus pneumoniae / Q000235:genetics / Q000302:isolation & purification; D013997:Time Factors