Two major Spanish clones of penicillin-resistant Streptococcus pneumoniae in Portuguese isolates of clinical origin

We studied the genetic relatedness of 47 Portuguese penicillin-resistant 9V and 23F Streptococcus pneumoniae of clinical origin, using pulsed-field gel electrophoresis (PFGE) and restriction fragment length polymorphism analysis. PFGE fingerprinting showed that 24 isolates of serotype 9V and 23 isolates of serotype 23F were variants of the Spain(9V)-3 and Spain(23F)-1 clones, respectively. Fingerprinting of pbp1a, pbp2b and pbp2x genes showed that all the penicillin-resistant clones gave similar HinfI restriction patterns. In this study, serotypes 9V and 23F have different clonal origins and identical PBP genotypes, suggesting a horizontal transfer of resistance. Visual and computer-assisted analysis of PFGE patterns correlated well (r = 0.983).