Penicillin-binding proteins of multiply antibiotic-resistant South African strains of Streptococcus pneumoniae.

Multiply drug-resistant South African pneumococci (with penicillin minimal inhibitory concentrations ranging from 0.2 to 12.5 microgram/ml) showed several types of major alterations in their penicillin-binding protein (PBP) pattern compared with that of a penicillin-susceptible laboratory strain of Streptococcus pneumoniae (R6; penicillin minimal inhibitory concentration = 0.006 microgram/ml). Genetic transformants were obtained by using South African pneumococcus (strain 8249) deoxyribonucleic acid as donor and the competent cells of strain R6 as recipient; seven classes of transformants with progressively higher penicillin resistance were isolated, and their PBPs were tested. The PBP patterns exhibited a gradual shift from a pattern similar to that of the recipient to a pattern resembling that of the donor strain as the level of penicillin resistance increased.