title: Hypermutable Haemophilus influenzae with mutations in mutS are found in cystic fibrosis sputum.
abstract: Hypermutable bacterial pathogens exist at surprisingly high prevalence and benefit bacterial populations by promoting adaptation to selective environments, including resistance to antibiotics. Five hundred Haemophilus influenzae isolates were screened for an increased frequency of mutation to resistance to rifampicin, nalidixic acid and spectinomycin: of the 14 hypermutable isolates identified, 12 were isolated from cystic fibrosis (CF) sputum. Analysis by enterobacterial repetitive intergenic consensus (ERIC)-PCR and ribotyping identified eight distinct genetic fingerprints. The hypermutable phenotype of seven of the eight unique isolates was associated with polymorphisms in conserved sites of mutS. Four of the mutant mutS alleles were cloned and failed to complement the mutator phenotype of a mutS : : TSTE mutant of H. influenzae strain Rd KW20. Antibiotic susceptibility testing of the hypermutators identified one beta-lactamase-negative ampicillin-resistant (BLNAR) isolate with two isolates producing beta-lactamase. Six isolates from the same patient with CF, with the same genetic fingerprint, were clonal by multilocus sequence typing (MLST). In this clone, there was an evolution to higher MIC values for the antibiotics administered to the patient during the period in which the strains were isolated. Hypermutable H. influenzae with mutations in mutS are prevalent, particularly in the CF lung environment, and may be selected for and maintained by antibiotic pressure.
authors.affiliation: Department of Molecular Microbiology and Immunology, School of Medicine, University of Missouri-Columbia, Columbia, MO 65212, USA.|Seattle Biomedical Research Institute, 307 Westlake Ave N, Suite 500, Seattle, WA 98109, USA.
authors.forename: Michael E
authors.initials: ME
authors.lastname: Watson
authors.affiliation: Division of Infectious Diseases, Children's Hospital and Regional Medical Center, 4800 Sand Point Way, Seattle, WA 98105, USA.
authors.forename: Jane L
authors.initials: JL
authors.lastname: Burns
authors.affiliation: Seattle Biomedical Research Institute, 307 Westlake Ave N, Suite 500, Seattle, WA 98109, USA.
authors.forename: Arnold L
authors.initials: AL
authors.lastname: Smith
mesh_terms: D000251:Adenosine Triphosphatases / Q000235:genetics* / Q000502:physiology*; D000668:Ampicillin Resistance; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics* / Q000502:physiology*; D003001:Cloning, Molecular; D003550:Cystic Fibrosis / Q000382:microbiology*; D016172:DNA Fingerprinting; D004269:DNA, Bacterial / Q000032:analysis / Q000737:chemistry / Q000302:isolation & purification; D021901:DNA, Intergenic; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000502:physiology*; D024881:Drug Resistance, Bacterial / Q000235:genetics; D005798:Genes, Bacterial; D005816:Genetic Complementation Test; D006193:Haemophilus influenzae / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification*; D006801:Humans; D008969:Molecular Sequence Data; D051719:MutS DNA Mismatch-Binding Protein; D009154:Mutation; D009268:Nalidixic Acid / Q000494:pharmacology; D011110:Polymorphism, Genetic; D012091:Repetitive Sequences, Nucleic Acid; D021521:Ribotyping; D012293:Rifampin / Q000494:pharmacology; D012641:Selection, Genetic; D017422:Sequence Analysis, DNA; D000198:Spectinomycin / Q000494:pharmacology; D013183:Sputum / Q000382:microbiology*; D001618:beta-Lactamases / Q000032:analysis
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D004269:DNA, Bacterial; D021901:DNA, Intergenic; D004268:DNA-Binding Proteins; D009268:Nalidixic Acid; D000198:Spectinomycin; D001618:beta-Lactamases; D000251:Adenosine Triphosphatases; D051719:MutS DNA Mismatch-Binding Protein; D012293:Rifampin