Sequential colonization by Streptococcus pneumoniae of healthy children living in an orphanage.

A prospective study of nasopharyngeal colonization by Streptococcus pneumoniae in the exceptional conditions of a closed community of abandoned children was done over a 1-year period; 71 children (age <24 months) were studied monthly. S. pneumoniae was isolated from 58 (81.7%), and 94.5% of the 111 isolates were resistant to penicillin. The mean rate of carriage was estimated at 57.4%, ranging from 42.8% to 70.4%. Children were sequentially colonized by a mean of 3 different isolates. The mean duration of carriage for a given isolate was approximately 2.2 months. Serotyping and molecular typing by pulsed-field gel electrophoresis showed that children were colonized by a limited number of clones belonging to only 4 serotypes and 4 pulsotypes. These clones rapidly spread in the community and colonized the children in waves, with a rapid turnover of S. pneumoniae isolates, facilitated by close contact between children.