title: Transfer of penicillin resistance from Streptococcus oralis to Streptococcus pneumoniae identifies murE as resistance determinant.
abstract: Beta-lactam resistant clinical isolates of Streptococcus pneumoniae contain altered penicillin-binding protein (PBP) genes and occasionally an altered murM, presumably products of interspecies gene transfer. MurM and MurN are responsible for the synthesis of branched lipid II, substrate for the PBP catalyzed transpeptidation reaction. Here we used the high-level beta-lactam resistant S. oralis Uo5 as donor in transformation experiments with the sensitive laboratory strain S. pneumoniae R6 as recipient. Surprisingly, piperacillin-resistant transformants contained no alterations in PBP genes but carried murEUo5 encoding the UDP-N-acetylmuramyl tripeptide synthetase. Codons 83-183 of murEUo5 were sufficient to confer the resistance phenotype. Moreover, the promoter of murEUo5 , which drives a twofold higher expression compared to that of S. pneumoniae R6, could also confer increased resistance. Multiple independent transformations produced S. pneumoniae R6 derivatives containing murEUo5 , pbp2xUo5 , pbp1aUo5 and pbp2bUo5 , but not murMUo5 sequences; however, the resistance level of the donor strain could not be reached. S. oralis Uo5 harbors an unusual murM, and murN is absent. Accordingly, the peptidoglycan of S. oralis Uo5 contained interpeptide bridges with one L-Ala residue only. The data suggest that resistance in S. oralis Uo5 is based on a complex interplay of distinct PBPs and other enzymes involved in peptidoglycan biosynthesis.
authors.affiliation: Department of Microbiology, University of Kaiserslautern, Kaiserslautern, Germany.
authors.forename: Katya
authors.initials: K
authors.lastname: Todorova
authors.affiliation: Department of Microbiology, University of Kaiserslautern, Kaiserslautern, Germany.
authors.forename: Patrick
authors.initials: P
authors.lastname: Maurer
authors.affiliation: Department of Microbiology, University of Kaiserslautern, Kaiserslautern, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Rieger
authors.affiliation: Department of Microbiology, University of Kaiserslautern, Kaiserslautern, Germany.
authors.forename: Tina
authors.initials: T
authors.lastname: Becker
authors.affiliation: Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle upon Tyne, NE2 4AX, UK.
authors.forename: Nhat Khai
authors.initials: NK
authors.lastname: Bui
authors.affiliation: Institute for Cell and Molecular Biosciences, Pinnacle Laboratory, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK.
authors.forename: Joe
authors.initials: J
authors.lastname: Gray
authors.affiliation: Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle upon Tyne, NE2 4AX, UK.
authors.forename: Waldemar
authors.initials: W
authors.lastname: Vollmer
authors.affiliation: Department of Microbiology, University of Kaiserslautern, Kaiserslautern, Germany.
authors.forename: Regine
authors.initials: R
authors.lastname: Hakenbeck
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics*; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics; D010403:Penicillin Resistance / Q000235:genetics*; D046915:Penicillin-Binding Proteins / Q000235:genetics; D010453:Peptide Synthases / Q000235:genetics; D010457:Peptidoglycan / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics; D010458:Peptidyl Transferases / Q000235:genetics; D010878:Piperacillin / Q000378:metabolism; D019533:Streptococcus oralis / Q000187:drug effects* / Q000235:genetics*; D013296:Streptococcus pneumoniae / Q000187:drug effects* / Q000235:genetics*; D014170:Transformation, Genetic; D047090:beta-Lactams / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D046915:Penicillin-Binding Proteins; D010457:Peptidoglycan; D047090:beta-Lactams; D010458:Peptidyl Transferases; D010453:Peptide Synthases; C049145:UDP-N-acetylmuramoylalanyl-D-glutamate-2,6-diaminopimelate ligase; D010878:Piperacillin