title: Vancomycin tolerance in clinical and laboratory Streptococcus pneumoniae isolates depends on reduced enzyme activity of the major LytA autolysin or cooperation between CiaH histidine kinase and capsular polysaccharide.
abstract: Vancomycin is frequently added to standard therapy for pneumococcal meningitis. Although vancomycin-resistant Streptococcus pneumoniae strains have not been isolated, reports on the emergence of vancomycin-tolerant pneumococci are a cause of concern. To date, the molecular basis of vancomycin tolerance in S. pneumoniae is essentially unknown. We examined two vancomycin-tolerant clinical isolates, i.e. a purported autolysin negative (LytA(-)), serotype 23F isolate (strain S3) and the serotype 14 strain 'Tupelo', which is considered a paradigm of vancomycin tolerance. S3 was characterized here as carrying a frameshift mutation in the lytA gene encoding the main pneumococcal autolysin. The vancomycin tolerance of strain S3 was abolished by transformation to the autolysin-proficient phenotype. The original Tupelo strain was discovered to be a mixture: a strain showing a vancomycin-tolerant phenotype (Tupelo_VT) and a vancomycin-nontolerant strain (Tupelo_VNT). The two strains differed only in terms of a single mutation in the ciaH gene present in the VT strain. Most interestingly, although the vancomycin tolerance of Tupelo_VT could be overcome by increasing the LytA dosage upon transformation by a multicopy plasmid or by externally adding the autolysin, we show that vancomycin tolerance in S. pneumoniae requires the simultaneous presence of a mutated CiaH histidine kinase and capsular polysaccharide.
authors.affiliation: Centro de Investigaciones Biológicas (CSIC) and Centro de Investigación Biomédica en Red de Enfermedades Respiratorias (CIBERES), Ramiro de Maeztu, 9, 28040 Madrid, Spain.
authors.forename: Miriam
authors.initials: M
authors.lastname: Moscoso
authors.affiliation: Centro de Investigaciones Biológicas (CSIC) and Centro de Investigación Biomédica en Red de Enfermedades Respiratorias (CIBERES), Ramiro de Maeztu, 9, 28040 Madrid, Spain.
authors.forename: Mirian
authors.initials: M
authors.lastname: Domenech
authors.affiliation: Centro de Investigaciones Biológicas (CSIC) and Centro de Investigación Biomédica en Red de Enfermedades Respiratorias (CIBERES), Ramiro de Maeztu, 9, 28040 Madrid, Spain.
authors.forename: Ernesto
authors.initials: E
authors.lastname: García
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004361:Drug Tolerance; D016368:Frameshift Mutation; D018628:Gene Dosage; D005816:Genetic Complementation Test; D000071677:Histidine Kinase; D008969:Molecular Sequence Data; D009238:N-Acetylmuramoyl-L-alanine Amidase / Q000235:genetics / Q000378:metabolism*; D011135:Polysaccharides, Bacterial / Q000378:metabolism*; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D017422:Sequence Analysis, DNA; D013290:Streptococcal Infections / Q000382:microbiology; D013296:Streptococcus pneumoniae / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics / Q000302:isolation & purification; D014640:Vancomycin / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; D011135:Polysaccharides, Bacterial; D014640:Vancomycin; D011494:Protein Kinases; D000071677:Histidine Kinase; D009238:N-Acetylmuramoyl-L-alanine Amidase