DIFFERENCES IN PENICILLIN-BINDING PROTEIN-PATTERNS OF PENICILLIN TOLERANT AND NONTOLERANT GROUP-A STREPTOCOCCI

The penicillin-binding proteins (PBPs) of five penicillin tolerant gro up A streptococci and their isogenic non-tolerant strains, and seven u nrelated non-tolerant group A streptococci were compared. PBPs from la te logarithmic cultures were labelled in vitro with H-3-benzylpenicill in and analysed by SDS-PAGE and fluorography. The PBP patterns for all non-tolerant strains were identical. This pattern differed markedly f rom that for penicillin tolerant strains, both qualitatively and quant itatively. The most striking change in penicillin tolerant strains was decreased binding of H-3-penicillin to PBP 3 and increased binding to PBP 5, while PBP 2a was replaced by a new PBP (PBP 2a') of lower elec trophoretic mobility. Tolerance was lost during storage but could be r estored by consecutive transfers on to penicillin gradient agar plates . At the same time the PBP profiles of these strains became identical to those found for stable tolerant strains. These results suggest the possibility that PBP 2a' and PBP 5 in combination with other PBP alter ations play a role in penicillin tolerance found in group A streptococ ci.