Penicillin-binding proteins in Streptococcus pneumoniae: alterations during development of intrinsic penicillin resistance.

Four out of the five high molecular weight penicillin-binding proteins (PBPs) of Streptococcus pneumoniae are involved in the development of intrinsic penicillin resistance. In beta-lactam resistant laboratory mutants, point mutations in the PBP 2x-genes were identified that result in low penicillin-affinity mutant proteins. In contrast, PBPs 1a, 2x, and 2b of resistant clinical isolates are highly altered as can be recognized biochemically and immunologically; DNA sequence analysis of the PBP 2x gene from resistant strains confirmed these results. The variability of the three PBPs analyzed implies a very heterogeneous gene pool accessible to the pneumococcus that is used for recruitment of resistant PBP genes in wild type strains.