Clones of Streptococcus pneumoniae isolated from nasopharyngeal carriage and invasive disease in young children in central Tennessee

To determine whether nasopharyngeal carriage isolates of Streptococcus pneu moniae are of the same genetic background as isolates that caused invasive disease in one community, IS1167 and boxA genotypes were obtained for 182 p neumococcal isolates from children living in central Tennessee. The isolate s represented 70 combined IS1167-boxA genotypes. The genotypic diversity of the invasive isolates was significantly less than that of the total popula tion (P=.003). Most of the carriage isolates belonged to genotypes unique t o carriage, whereas most of the invasive isolates belonged to genotypes com mon to carriage and disease (P = .02). Monte Carlo simulations showed a gre ater number of genotypes unique to carriage than can be explained by chance (P<.05 in all cases). Two genotypes were identified by multilocus sequence typing as members of globally disseminated clones, and one such genotype t hat was strictly carriage in this sample caused disease in other studies. T hus, clones can have different propensities for carriage and invasion.