The alteration of penicillin-binding proteins (PBPs) in drug-resistant Streptococcus pneumoniae isolated from acute otitis media

Streptococcus pneumoniae is the micro-organism most frequently isolated fro m acute otitis media (AOM). Recently, drug-resistant or insensitive strains have been prevalent among pneumococcal AOM cases and were reportedly assoc iated with persistent or recurrent otitis media. The purpose of this study was to examine the alterations of penicillin-binding proteins (PBPs) in Str eptococcus pneumoniae isolated from AOM. The PBP samples from 21 clinically isolated strains were examined by C-14-penicillin binding assay and also b y adding CCL and CDTR as competitors of C-14-penicillin. Reduced signals in PBP1A and PBP2X/2A were typically observed with the penicillin-resistant S treptococcus pneumoniae samples, while widely different PBP profiles were o btained in each strain of penicillin-insensitive Streptococcus pneumoniae. The competitive binding assay with penicillin-insensitive strains revealed the reduced affinity of CCL to PBPs in comparison with that of CDTR. The re sults of the penicillin-binding assay were consistent with the results from minimal inhibitory concentration analysis, and its potential usefulness fo r the prediction of drug resistance was demonstrated.