title: Frequency of mutation to rifampin resistance in Streptococcus pneumoniae clinical strains: hexA and hexB polymorphisms do not account for hypermutation.
abstract: The frequency of mutation to rifampin resistance of 200 clinical Streptococcus pneumoniae isolates was examined. Two peaks were observed in the distribution, with mode frequencies of 2.5 x 10(-7) (20% of isolates) and 2.5 x 10(-8). The hexA and hexB gene entire sequences were analyzed in 13 isolates. Sequences from both hypermutable and "normomutable" strains were conserved relative to that of the R6 S. pneumoniae control strain. The phenotypic Hex system proficiency, in terms of transforming efficiency, was also maintained irrespective of the variations in mutation frequency values.
authors.affiliation: Servicio de Microbiología, Hospital Universitario Ramón y Cajal, Madrid, Spain. mmorosini.hrc@salud.madrid.org
authors.forename: María-Isabel
authors.initials: MI
authors.lastname: Morosini
authors.forename: María-Rosario
authors.initials: MR
authors.lastname: Baquero
authors.forename: J M
authors.initials: JM
authors.lastname: Sánchez-Romero
authors.forename: María-Cristina
authors.initials: MC
authors.lastname: Negri
authors.forename: Juan-Carlos
authors.initials: JC
authors.lastname: Galán
authors.forename: Rosa
authors.initials: R
authors.lastname: del Campo
authors.forename: J C
authors.initials: JC
authors.lastname: Pérez-Díaz
authors.forename: Fernando
authors.initials: F
authors.lastname: Baquero
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000235:genetics*; D009154:Mutation; D011110:Polymorphism, Genetic; D012293:Rifampin / Q000494:pharmacology*; D013296:Streptococcus pneumoniae / Q000187:drug effects* / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; C084499:HexA protein, bacteria; D012293:Rifampin