Alterations to penicillin-binding proteins 1A, 2B and 2X amongst penicillin-resistant clinical isolates of Streptococcus pneumoniae serotype 23F fromthe nasopharyngeal flora of children

Various amino acid substitutions were identified in the three major penicil lin-binding proteins (PBP1A, PBP2B and PBP2X) of eight clinical isolates of Streptococcus pneumoniae serotype 23F collected from children. The particu lar changes related to the level of penicillin resistance. Alterations were detected in an isolate with a penicillin MIC as low as 0.06 mg/L. These re sults confirm that the level of penicillin resistance in pneumococci reflec ts with sequential alterations of PBPs in clinical isolates.