Clonal distribution of penicillin-resistant Streptococcus pneumoniae 23F in France.

We studied the clonality of clinical isolates of Streptococcus pneumoniae 23F, the serotype most often associated with penicillin resistance in France. Clinical isolates obtained between November 1992 and April 1993 from nasopharyngeal samples from children with acute otitis media from different regions of the country were analyzed. The genetic polymorphism of penicillin-susceptible and -resistant 23F isolates (MIC, 2 mg/liter) was studied by pulsed-field gel electrophoresis. The resistant isolates were closely related, whereas the susceptible isolates were genetically heterogeneous. PCR amplification and restriction of the genes encoding penicillin-binding proteins (PBPs) 1A, 2B, and 2X also showed that the 24 resistant isolates had similar patterns which were very different from those of the susceptible isolates. All resistant isolates gave the same PBP pattern, with low affinities of PBPs for penicillin. Our results indicate that, in contrast to penicillin-susceptible 23F isolates, the penicillin-resistant 23F isolates have a single clonal origin, suggesting the rapid clonal spread of a resistant epidemic strain throughout the country.