title: Penicillin-resistant and penicillin-tolerant mutants of group A Streptococci.
abstract: Penicillin-resistant and penicillin-tolerant mutants have been isolated from group A streptococci mutagenized by ethyl methane sulfonate. The resistant mutants had an elevated minimal growth inhibitory concentration for benzylpenicillin (minimal inhibitory concentration, 0.2 microgram/ml, as compared with the minimal inhibitory concentration of 0.006 microgram/ml in the penicillin-susceptible parent strain); they also had an abnormal cellular morphology and showed altered penicillin-binding proteins. Penicillin-tolerant mutants were killed more slowly than were the parental cells during treatment with penicillin; they had virtually unchanged minimal inhibitory concentration values for penicillin and normal cellular morphology and penicillin-binding proteins.
mesh_terms: D001426:Bacterial Proteins; D002352:Carrier Proteins / Q000378:metabolism; D006602:Hexosyltransferases; D002267:Muramoylpentapeptide Carboxypeptidase; D009154:Mutation; D010403:Penicillin Resistance; D046915:Penicillin-Binding Proteins; D010406:Penicillins / Q000494:pharmacology*; D010458:Peptidyl Transferases; D012329:RNA, Bacterial / Q000096:biosynthesis; D013297:Streptococcus pyogenes / Q000187:drug effects*; D013997:Time Factors
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D046915:Penicillin-Binding Proteins; D010406:Penicillins; D012329:RNA, Bacterial; D010458:Peptidyl Transferases; D006602:Hexosyltransferases; D002267:Muramoylpentapeptide Carboxypeptidase