title: Penicillin-binding proteins as resistance determinants in clinical isolates of Streptococcus pneumoniae.
abstract: Altered penicillin-binding proteins (PBPs) with reduced affinity for penicillin are encoded by mosaic genes in penicillin-resistant clinical isolates of Streptococcus pneumoniae. Generally, members of one bacterial clone contain the same mosaic gene. We report here on a serotype 19A clone of penicillin- and multiple-resistant S. pneumoniae prevalent in Hungary, members of which are exceptionally diverse in terms of PBP properties. The pbp2x gene of four 19A isolates was sequenced, and a distinct mosaic structure detected in each case. The pbp2x genes also differed from a homologous gene of a high-level penicillin-resistant S. mitis from Hungary. The contribution of PBPs to resistance development was studied on transformation experiments using the laboratory strain R6 as recipient, and PBP genes from the type 19A isolate Hu11. pbp2x and pbp2b function as primary resistance determinants for different beta-lactams. Secondary transformation with pbp1a increased the resistance level considerably for penicillins and cefotaxime. Chromosomal DNA of a high-level penicillin- and cefotaxime-resistant S. mitis from Hungary also transformed the R6 strain to increased resistance levels, and PBP2x and PBP2b functioned as primary resistance determinants as above. In contrast, high-level cefotaxime resistance appeared to be due to a low affinity PBP2a, indicating that this PBP can also function as a resistance determinant.
authors.affiliation: Max-Planck Institut für molekulare Genetik, Berlin, Germany.
authors.forename: P
authors.initials: P
authors.lastname: Reichmann
authors.forename: A
authors.initials: A
authors.lastname: König
authors.forename: A
authors.initials: A
authors.lastname: Marton
authors.forename: R
authors.initials: R
authors.lastname: Hakenbeck
mesh_terms: D019881:Aminoacyltransferases; D001426:Bacterial Proteins; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002439:Cefotaxime / Q000494:pharmacology; D002511:Cephalosporins / Q000494:pharmacology; D003001:Cloning, Molecular; D004269:DNA, Bacterial / Q000737:chemistry; D018432:Drug Resistance, Multiple / Q000235:genetics; D005798:Genes, Bacterial; D006602:Hexosyltransferases; D006801:Humans; D006814:Hungary; D008969:Molecular Sequence Data; D002267:Muramoylpentapeptide Carboxypeptidase / Q000235:genetics / Q000378:metabolism*; D010403:Penicillin Resistance / Q000235:genetics; D046915:Penicillin-Binding Proteins; D010453:Peptide Synthases; D010458:Peptidyl Transferases; D011008:Pneumococcal Infections / Q000188:drug therapy / Q000382:microbiology*; D016133:Polymerase Chain Reaction; D013296:Streptococcus pneumoniae / Q000187:drug effects* / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D002511:Cephalosporins; D004269:DNA, Bacterial; D046915:Penicillin-Binding Proteins; C478699:penicillin-binding protein 2a, Streptococcus; D019881:Aminoacyltransferases; C478701:penicillin-binding protein 2b, Streptococcus; D010458:Peptidyl Transferases; D006602:Hexosyltransferases; D002267:Muramoylpentapeptide Carboxypeptidase; D010453:Peptide Synthases; D002439:Cefotaxime