Isolate differences in colonization efficiency during experimental human pneumococcal challenge

Abstract

SummaryColonization efficiency varies considerably between Streptococcus pneumoniae (pneumococcus) strains. The microbial characteristics that influence those differences are still largely unknown. Here, we report rates and kinetics of colonization of four pneumococcal strains upon experimental human pneumococcal challenge. Healthy adults were intranasally challenged with one of four pneumococcal strains (serotype/clonal name: 6B/BHN418, 15B/SH8286, 23F/P1121 and 23F/P833) over a range of doses. Maximum colonization achieved was 60%, 31%, 16% and 10%, respectively. Density and duration of colonization did not differ significantly between the tested strains. We further evaluated murine colonization, non-opsonic neutrophil mediated killing, epithelial cell adherence and average chain length of these four pneumococcal strains. Of these, only chain length was found to be associated with colonization efficiency in the human challenge model. Our data demonstrate that colonization rates following experimental challenge vary with the strain used and suggest that efficiency in colonization is related to pneumococcal chain length.