title: Population biology of Streptococcus pneumoniae isolated from oropharyngeal carriage and invasive disease.
abstract: The population structure of Streptococcus pneumoniae in a sample of 134 carried antibiotic-susceptible isolates, and 53 resistant and susceptible invasive isolates, was examined using a DNA-based version of multilocus enzyme electrophoresis: multilocus restriction typing (MLRT). This involved RFLP analysis of PCR products generated from nine loci of housekeeping genes located around the pneumococcal chromosome. The combination of alleles at each of the nine loci gave an allelic profile or restriction type (RT). All carried (throat or nasopharyngeal) isolates from children or adults in Oxford and Manchester, UK, and from an HIV-seropositive cohort in Nairobi, Kenya, showed an epidemic population structure. Twelve carried clonal groups, each with different serotypes, were identified at both locations within the UK. Almost all of the carried clones examined (16/17) were found to possess identical RTs or sequence types (STs) to invasive isolates, indicating that frequently carried clones are also associated with cases of invasive disease. As expected from previous studies, the population of 53 invasive, mainly penicillin-resistant, isolates was also found to be at linkage equilibrium. Serotype switching was identified among 14% of RTs that possessed two or more members, or 5.7% of individual isolates within these RTs. In support of a population structure in which there is frequent recombination, there is also clear evidence that the trpA/B locus within pneumococci has evolved by horizontal gene transfer. A non-serotypable isolate from an HIV-seropositive patient in Kenya was clearly genetically distinct from other strains studied, with unique alleles at eight out of nine loci examined. However, it was initially identified as a pneumococcus by a 16S RNA gene probe (Gen-Probe), optochin susceptibility and the presence of pneumolysin and autolysin.
authors.affiliation: Department of Biological Sciences, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK1.
authors.forename: Christine D M
authors.initials: CDM
authors.lastname: Müller-Graf
authors.affiliation: Department of Biological Sciences, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK1.
authors.forename: Adrian M
authors.initials: AM
authors.lastname: Whatmore
authors.affiliation: Department of Biological Sciences, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK1.
authors.forename: Samantha J
authors.initials: SJ
authors.lastname: King
authors.affiliation: Department of Biological Sciences, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK1.
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Trzcinski
authors.affiliation: Department of Biological Sciences, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK1.
authors.forename: A Paul
authors.initials: AP
authors.lastname: Pickerill
authors.affiliation: Department of Biological Sciences, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK1.
authors.forename: Neil
authors.initials: N
authors.lastname: Doherty
authors.affiliation: Public Health Laboratory, Royal Sussex County Hospital, Brighton BN2 5BE, UK2.
authors.forename: John
authors.initials: J
authors.lastname: Paul
authors.affiliation: John Radcliffe Hospital, Headington, Oxford OX3 9DU, UK3.
authors.forename: David
authors.initials: D
authors.lastname: Griffiths
authors.affiliation: John Radcliffe Hospital, Headington, Oxford OX3 9DU, UK3.
authors.forename: Derek
authors.initials: D
authors.lastname: Crook
authors.affiliation: Department of Biological Sciences, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK1.
authors.forename: Christopher G
authors.initials: CG
authors.lastname: Dowson
mesh_terms: D000293:Adolescent; D000328:Adult; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D015373:Bacterial Typing Techniques; D001483:Base Sequence; D002353:Carrier State / Q000453:epidemiology / Q000382:microbiology*; D002648:Child; D002675:Child, Preschool; D004352:Drug Resistance, Microbial; D005260:Female; D005798:Genes, Bacterial / Q000235:genetics; D014644:Genetic Variation; D005828:Genetics, Population; D006679:HIV Seropositivity; D006801:Humans; D017720:Molecular Epidemiology; D008969:Molecular Sequence Data; D009960:Oropharynx / Q000382:microbiology*; D011008:Pneumococcal Infections / Q000453:epidemiology / Q000382:microbiology*; D012150:Polymorphism, Restriction Fragment Length; D013296:Streptococcus pneumoniae / Q000145:classification* / Q000187:drug effects / Q000235:genetics; D014774:Virulence
chemical_list: D000900:Anti-Bacterial Agents