title: Alterations in penicillin-binding proteins of clinical and laboratory isolates of pathogenic Streptococcus pneumoniae with low levels of penicillin resistance.
abstract: Several recent surveys of clinical isolates have indicated that substantial fractions of naturally occurring populations of Streptococcus pneumoniae have undergone a distinct upward move in the required minimal inhibitory concentration (MIC) of benzylpenicillin (from a range of 0.006-0.008 to 0.03-0.05 microgram/ml). Evidence is presented that in clinical pneumococcal isolates, penicillin-binding proteins (PBPs) groups 1 and 2 have a decreased affinity for radioactive benzylpenicillin as compared with penicillin-sensitive isolates from the same locale. Exposure of a penicillin-sensitive type 2 strain (MIC, 0.006 microgram/ml) to sequentially increasing concentrations of penicillin allowed the isolation of spontaneous resistant mutants with stepwise increases in the MIC of penicillin required (0.01-0.02, 0.025-0.05, and 0.1 microgram/ml), and in these laboratory isolates too, PBP groups 1 and 2 showed decreased affinity for labeled benzylpenicillin. DNA from the low-level resistant clinical or laboratory isolates could be used to transform the appropriate levels of penicillin resistance into penicillin-sensitive laboratory isolates. These findings suggest that significant fractions of natural pneumococcal populations may have acquired one or two of the low-level penicillin resistance genes.
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D002268:Carboxypeptidases / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism*; D004269:DNA, Bacterial / Q000235:genetics; D006602:Hexosyltransferases; D006801:Humans; D008970:Molecular Weight; D002267:Muramoylpentapeptide Carboxypeptidase / Q000378:metabolism*; D009154:Mutation; D010403:Penicillin Resistance; D046915:Penicillin-Binding Proteins; D010406:Penicillins / Q000378:metabolism*; D010458:Peptidyl Transferases; D013296:Streptococcus pneumoniae / Q000187:drug effects* / Q000378:metabolism / Q000472:pathogenicity; D014170:Transformation, Genetic
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D004269:DNA, Bacterial; D046915:Penicillin-Binding Proteins; D010406:Penicillins; D010458:Peptidyl Transferases; D006602:Hexosyltransferases; D002268:Carboxypeptidases; D002267:Muramoylpentapeptide Carboxypeptidase