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R K Selander

Publications and source records attributed to R K Selander.

At least 91 records · Page 5Linked to original sources
PubMed1988

Characterization of P fimbriae on O1, O7, O75, rough, and nontypable strains of Escherichia coli.

P fimbriae of 37 uropathogenic Escherichia coli O1:K1, O7:K1, O22, O75, rough:K1, and nontypable strains were characterized by immunoprecipitation with 14 fimbria-specific rabbit antisera. The fimbrial composition of these strains, as reflected by the apparent molecular weights of the fimbrial peptides, was correlated with the O serogroup of the strains, but serological cross-reactivity of P fimbriae of different E. coli serogroups was frequently observed. The genetic clonal relationships of the strains were analyzed by determining the electrophoretic types, based on 18 chromosomally encoded enzymes. Among the O1:K1 strains, the same P-fimbrial variants occurred on strains that were either closely related or very distinct in their electrophoretic types, indicating that the P fimbriae have evolved in association with the O and K antigens. In contrast, certain O7:K1 and R:K1 strains as well as some O22 and O75 strains were genotypically identical and shared similar P-fimbrial variants, which differed serologically from those of other E. coli serogroups. Our results show that, despite the structural variability seen in electrophoretic analysis of P fimbriae of different serogroups, many P-fimbrial variants share common antigenic determinants that are recognized by rabbit antisera. Based on immunoprecipitation analyses, three anti-P-fimbria sera have now been identified that react with P fimbriae of 82 of 84 uropathogenic E. coli strains characterized in Finland.

Bacterial Adhesion↗
PubMed1988

Clonal population structure of encapsulated Haemophilus influenzae.

Chromosomal genotypes of 2,209 isolates of the six polysaccharide capsule types of Haemophilus influenzae recovered from human hosts worldwide were characterized by an analysis of electrophoretically demonstrable allelic profiles at 17 metabolic enzyme loci. For 222 representative isolates, restriction fragment length polymorphism patterns produced by digestion of cap region DNA were also determined. With few exceptions, isolates belonging to individual phylogenetic lines or groups of allied lineages identified by multilocus enzyme electrophoresis had characteristic cap region restriction fragment length polymorphism patterns and characteristic combinations of cap region patterns and outer membrane protein types. The occurrence of strong associations of characters and the recovery of isolates with identical genetic properties in widely separated geographic regions and over a 40-year period indicated that the population structure of encapsulated H. influenzae is clonal. Recombination of chromosomal genes, including those mediating capsule synthesis, apparently is not a major factor in the short-term evolution of these pathogenic organisms and, therefore, may be of minor clinical significance.

Bacterial Outer Membrane Proteins↗
PubMed1988

Clonal diversity of Neisseria meningitidis from a population of asymptomatic carriers.

Genetic diversity and relationships among 109 isolates of Neisseria meningitidis obtained from throat cultures of healthy individuals in Norway in 1984 were assessed by analyzing electrophoretically demonstrable allelic variation at 15 enzyme-encoding chromosomal genes. Seventy-eight distinctive electrophoretic types (ETs), representing multilocus genotypes, were identified. The mean genetic diversity per locus among the 78 ETs (0.538) was equivalent to that among 19 ETs represented by 66 isolates collected from patients with meningococcal disease in Norway in the first 5 months of 1984. The clonal composition of the collection of carrier strains was, however, quite different from that of strains from patients. The two groups of clones, the ET-5 complex and the ET-37 complex, that were responsible for 91% of the cases of systemic disease in Norway in 1984 were identified in only 7 and 9%, respectively, of the throat cultures from healthy individuals, and their frequencies in the human population sampled were only 0.7% for clones of the ET-5 complex and 0.9% for those of the ET-37 complex. The complex of clones that was most frequently represented by isolates from carriers (19%) has never been recovered from patients with meningococcal disease in Norway or elsewhere, which suggests that these clones have a low virulence potential. Children attending the same day care center or school seldom harbored the same clone in their throats.

Age Factors↗
PubMed1988

Legionella pneumophila serogroup Lansing 3 isolated from a patient with fatal pneumonia, and descriptions of L. pneumophila subsp. pneumophila subsp. nov., L. pneumophila subsp. fraseri subsp. nov., and L. pneumophila subsp. pascullei subsp. nov.

Previous DNA relatedness and enzyme electrophoretic mobility studies indicated heterogeneity among strains of Legionella pneumophila serogroups 1, 4, 5, and Lansing 3 (a new, as yet unnumbered serogroup). In this study 60 L. pneumophila strains were studied by DNA hybridization (hydroxyapatite method) to assess their genomic relatedness. These strains were also studied biochemically and serologically to determine whether they formed one or more phenotypic groups. DNA relatedness studies identified three groups. DNA group 1 contained the type strain Philadelphia 1 and strains from serogroups 1 through 14 of L. pneumophila. The average relatedness of DNA group 1 strains was 88% at 60 degrees C with 1.1% divergence in related sequences and 85% at 75 degrees C. DNA group 2 contained strain Los Angeles 1, the reference strain of serogroup 4, and strains of serogroups 1, 4, 5, and Lansing 3, an unnumbered serogroup. Average relatedness of DNA group 2 strains was 84% at 60 degrees C with 0.7% divergence and 87% at 75 degrees C. Reciprocal relatedness of DNA groups 1 and 2 was approximately 67% at 60 degrees C with 6.0% divergence and 48% at 75 degrees C. DNA group 3 strains were in serogroup 5. They were 98% related at 60 degrees C with 0.5% divergence and 97% related at 75 degrees C. Reciprocal relatedness of DNA group 3 and DNA group 1 was approximately 74% at 60 degrees C with 5.3% divergence and 43% at 75 degrees C, and reciprocal relatedness of DNA groups 3 and 2 was 66% at 60 degrees C with 5.7% divergence and 55% at 75 degrees C. The DNA groups could not be separated biochemically or serologically or by cell wall fatty acid and isoprenoid quinone composition. Three subspecies of L. pneumophila are proposed to accommodate the three DNA groups: L. pneumophila subsp. pneumophila subsp. nov. for DNA group 1, L. pneumophila subsp. fraseri subsp. nov. for DNA group 2, and pneumophila subsp. pascullei subsp. nov. for DNA group 3.

DNA, Bacterial↗
PubMed1987

Intercontinental spread of Neisseria meningitidis clones of the ET-5 complex.

The genetic structure of populations of Neisseria meningitidis was examined by an analysis of electrophoretically demonstrable allelic variation at 15 structural genes encoding enzymes in 688 isolates. Variation among strains in serogroup and serotype has little relationship to the complex structure of populations revealed by enzyme electrophoresis, which involves 14 major lineages of clones diverging from one another at more than half their genetic loci. Clones of one of these lineages, the ET-5 complex, have been identified as the causative agent of recent outbreaks and epidemics of meningococcal disease in Europe, South Africa, Latin America, and the United States. There is evidence that organisms of the ET-5 complex reached Florida via human immigrants from Cuba.

Cuba↗
PubMed1987

Large scale patterns of genetic differentiation at enzyme loci in the land snails Cepaea nemoralis and Cepaea hortensis.

Samples of 231 populations of the land snails Cepaea nemoralis and C. hortensis from Britain, France, Switzerland and Spain were analysed for genetic polymorphism in six enzyme systems. These sibling species show similar levels of variation detected by electrophoresis, and have a generally similar degree of local divergence over homologous enzyme loci. As well as extensive local and regional differentiation, both species show large-scale changes in allele frequency across Europe. In C. hortensis there is a continuous gradient in allele frequency from northern Britain to northern Spain, while in C. nemoralis north-south clines on the continent of Europe are reversed in direction in Britain. There are few obvious correlations of allele frequency change at single loci with components of the environment. Patterns of allele frequency variation in 24 sympatric populations of the two species are generally independent of each other, although there is a positive association of the frequencies of alleles at a leucine aminopeptidase locus in the two species. The statistical significance of this association depends on a single locality, and there is little indication of shared patterns of allele frequency change which might reflect a common response to natural selection. In addition, there is no evidence that the extensive geographical change in C. nemoralis and C. hortensis is a precursor of speciation.

Alleles↗
PubMed1987

Molecular Epidemiology of multiply resistant Haemophilus influenzae type b in day care centers.

We studied the molecular epidemiology of multiply resistant Haemophilus influenzae type b in four day care centers after each had a case of invasive infection due to organisms resistant to four or more antibiotics. Colonization rates among 174 childhood contacts and 27 employees of the four separate day care centers were 28% in children (range, 13.5%-43.7%) and 22% (range, 18.7%-33.0%) in employees. All strains were type b, were biotype I, were type 12 by isoenzyme analysis, and harbored plasmids whose mass was 45 or 52 megadaltons. Restriction endonuclease analysis indicated that the plasmids were closely related to one another but that there were at least three distinct plasmids. The four index strains had two different outer membrane protein profiles and three distinct plasmid restriction patterns; an additional outer membrane protein profile and plasmid restriction pattern were found in carrier strains.

Adult↗
PubMed1987

Genetic and phenotypic diversity among ampicillin-resistant, non-beta-lactamase-producing, nontypeable Haemophilus influenzae isolates.

Levels of genotypic and phenotypic diversity among 23 ampicillin-resistant, non-beta-lactamase-producing (Ampr NBLP) isolates of serologically nontypeable Haemophilus influenzae recovered from the respiratory tract were determined by multilocus enzyme electrophoresis, auxotroph testing in chemically defined media, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis of penicillin-binding proteins (PBPs). Twenty distinctive multilocus enzyme genotypes were identified, among which the average level of genetic diversity per locus was equivalent to that in the species as a whole. Hence, a single, recent origin for Ampr NBLP strains is excluded. Of the growth factors tested, a requirement for methionine was significantly associated with the Ampr NBLP phenotype. In contrast to the relative homogeneity of the PBP profiles of the ampicillin-susceptible strains tested (8 PBPs detected), the PBP profiles of the Ampr NBLP strains exhibited marked heterogeneity (5 to 10 PBPs detected). Care should be taken in interpreting changes in PBP profiles and in associating these profiles with resistance for species such as H. influenzae that demonstrate variability.

Alleles↗
PubMed1987

Clonal diversity in Haemophilus pleuropneumoniae.

Genetic diversity among 135 isolates of nine serotypes of Haemophilus pleuropneumoniae recovered from pigs with pleuropneumonia or other invasive diseases in 14 countries was estimated by multilocus enzyme electrophoresis, which detects allelic variation in structural genes. Thirty-two multilocus genotypes (electrophoretic types [ETs]) were distinguished on the basis of allele profiles at 15 enzyme loci, and 36 distinctive combinations of ET and serotype were identified. The recovery of isolates with identical properties in widely separated geographic regions and over a 20-year period indicated that the population structure of H. pleuropneumoniae is clonal. Isolates of the same ET generally shared the same serotype and electrophoretic pattern of the outer membrane proteins, but some ETs were represented by isolates of several different serotypes, outer membrane protein patterns, or both. On average, the genetic diversity among ETs of the same serotype was 56% of the total genetic diversity in the species. Isolates of serotype 1, which are unusually pathogenic, belong to a distinctive group of clones that are closely related to clones marked by serotype 9.

Alleles↗
PubMed1987

Genetic relationships and clonal population structure of serotype 2 strains of Neisseria meningitidis.

Two hundred and thirty-four strains of Neisseria meningitidis, including 94 serotype 2a, 111 serotype 2b, and 19 serotype 2c isolates, together with 10 isolates that were serotyped as 2 with polyvalent antiserum but did not react with monoclonal antibodies, were characterized by the electrophoretic mobilities of 15 metabolic enzymes. Of these enzymes, 14 were polymorphic, and 56 distinctive combinations of alleles at the enzyme loci (electrophoretic types) were identified, among which the mean genetic diversity per locus was 0.413, or about 75% of that recorded for the species N. meningitidis as a whole. Mean genetic diversity among electrophoretic types of the same serotype (2a, 2b, or 2c) was, however, on average, less than half the total species diversity, and no multilocus genotypes were shared between isolates of the different serotypes, which belong to distinctive clonal lineages. Recent temporal changes in the frequencies of recovery of pathogenic strains of serotypes 2a and 2b in South Africa and North America resulted from clone replacement in these populations rather than evolutionary modification of the serotype protein of the initially dominant clones.

Genetic Variation↗
PubMed1987

Genetic relationships among the oral streptococci.

Genetic relationships and species limits among the oral streptococci were determined by an analysis of electrophoretically demonstrable variation in 16 metabolic enzymes. Fifty isolates represented 40 electrophoretic types, among which the mean genetic diversity per locus was 0.857. Mannitol-1-phosphate dehydrogenase was not detected in isolates of the sanguis species complex, and glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase were absent in species of the mutans complex. Clustering from a matrix of Gower's coefficient of genetic similarity placed the 40 electrophoretic types in 10 well-defined groups corresponding to the Streptococcus species S. mutans, S. sobrinus, S. cricetus, S. rattus, S. ferus, S. oralis (mitior), two distinct assemblages of S. sanguis strains, and two subdivisions of "S. milleri." The assignments of isolates to these groups were the same as those indicated by DNA hybridization experiments, and the coefficient of correlation between genetic distance estimated by multilocus enzyme electrophoresis and genetic similarity indexed by DNA hybridization was -0.897 (P less than 0.001) for 50 pairwise combinations of isolates. S. ferus, which is widely believed to be a member of the mutans complex, was shown to be phylogenetically closer to species of the sanguis complex.

Animals↗
PubMed1987

Genetic structure of Neisseria meningitidis populations in relation to serogroup, serotype, and outer membrane protein pattern.

The genetic structure of populations of Neisseria meningitidis was examined by an analysis of electrophoretically demonstrable allelic variation at 15 genes encoding enzymes in 650 isolates of eight serogroups (A, B, C, W135, X, Y, Z, and 29E) and 38 nonserogroupable isolates. A total of 331 distinctive multilocus genotypes (electrophoretic types, ETs) was identified, among which mean genetic diversity per locus (H = 0.547) was greater than in Escherichia coli and other bacterial species thus far studied. The intercontinental distribution of some ETs and the recovery of organisms of identical genotype over periods of many years strongly suggest that the genetic structure of N. meningitidis is basically clonal as a consequence of low rates of recombination of chromosomal genes. Variation among strains in serogroup, serotype, and the electrophoretic pattern of the major outer membrane proteins has little relationship to the complex structure of populations revealed by enzyme electrophoresis, which involves 14 major lineages of clones diverging from one another at genetic distances greater than 0.50. Genetic diversity among ETs of isolates of the same serogroup was, on average, 84% of that in the total sample. Clones of serogroup A were unusual in being genotypically less heterogeneous than those of other serogroups and in forming a single phylogenetic group. Isolates of the same serotype or outer membrane protein pattern were also highly heterogeneous; on average, 87 and 97%, respectively, of the total species diversity was represented by ETs of the same serotype or outer membrane protein.

Bacterial Outer Membrane Proteins↗
PubMed1987

Clonal diversity and host distribution in Bordetella bronchiseptica.

A total of 303 isolates of Bordetella bronchiseptica recovered from 11 host species were characterized by the electrophoretic mobilities of 15 metabolic enzymes, and 21 distinctive multilocus genotypes (electrophoretic types) were distinguished on the basis of allele profiles at the enzyme loci. The population structure of B. bronchiseptica is clonal, and its genetic diversity is limited in comparison with most other pathogenic bacteria, perhaps reflecting a relatively recent origin of the species. Electrophoretic types mark clones which are, in many cases, nonrandomly associated with host species. Clones differing only slightly in overall chromosomal genetic character may have pronounced differences in virulence potential. There was considerable variation among individual clones and clone families in degree of host specificity and among various species of hosts in the diversity of clones causing disease. The diversity of clones infecting dogs was an order of magnitude greater than that of clones infecting pigs. Most bordetellosis in pigs in the United States and Japan was found to be caused by strains of a single multilocus genotype.

Animal Diseases↗
PubMed1987

Identification of Haemophilus influenzae type b by a monoclonal antibody coagglutination assay.

A coagglutination assay using monoclonal antibody is described for the identification of Haemophilus influenzae type b. An immunoglobulin G2a monoclonal antibody, Hb-2, directed against a serotype-specific outer membrane protein of H. influenzae type b was adsorbed to Staphylococcus aureus Cowan 1 cells. In a dot enzyme immunoassay, Hb-2 reacted with 453 of 455 H. influenzae type b isolates and did not react with H. influenzae of other serotypes, untypeable H. influenzae strains, or other bacterial species. The Hb-2 coagglutination assay was evaluated by testing 136 H. influenzae type b strains selected on the basis of multilocus enzyme genotypes, 5 strains of another serotype, and 94 untypeable H. influenzae strains. The specificity of the coagglutination assay was demonstrated by the inhibition of the reaction by free Hb-2 monoclonal antibodies. The coagglutination assay was as specific as the dot enzyme immunoassay and can be rapidly performed and easily interpreted.

Agglutination Tests↗
PubMed1986

Intercontinental spread of a genetically distinctive complex of clones of Neisseria meningitidis causing epidemic disease.

Strains of Neisseria meningitidis responsible for an epidemic of meningococcal disease occurring in Norway since the mid-1970s and for recent increases in the incidence of disease in several other parts of Europe have been identified by multilocus enzyme electrophoresis as members of a distinctive group of 22 closely related clones (the ET-5 complex). Clones of this complex have also colonized South Africa, Chile, Cuba, and Florida, where they have been identified as the causative agents of recent outbreaks of meningococcal disease. There is strong circumstantial evidence that outbreaks of disease occurring in Miami in 1981 and 1982 were caused in large part by bacteria that reached Florida via human immigrants from Cuba.

Disease Outbreaks↗
PubMed1986

Clonal analysis of Escherichia coli O2:K1 isolated from diseased humans and animals.

Forty-six Escherichia coli isolates of serotype O2:K1 from human urinary tract infections, chicken sepsis, and bovine mastitis were obtained from laboratories in England, Denmark, Sweden, and Finland. The bacteria were compared for outer membrane protein (OMP) pattern, lipopolysaccharide pattern, electrophoretic mobilities of enzymes, and flagellar serotype and were tested for fimbriation, biotype, hydroxamate production, hemolysin production, antibiotic resistance, plasmid content, colicin production, and virulence in neonatal rats. Isolates from humans were assigned to two clonal groups; poultry isolates belonged to one of these clonal groups, whereas bovine isolates belonged to the other. Poultry and human isolates of the same clonal group could be distinguished only by their plasmid content. Strains within this group were heterogeneous with respect to biotype, fimbriation, virulence, and flagellar serotype. Human and bovine isolates of the second clonal group were distinguished by a minor change in OMP pattern and by their plasmid content. It is concluded that meaningful clonal groupings are best recognized by the combination of OMP and electrophoretic enzyme patterns. The O:K serotype can aid in the recognition of important subclones, whereas the other microbiological properties tested can vary widely within clonal groupings. Furthermore, we conclude that certain O:K serotypes can contain very different clonal groupings having little genetic relatedness.

Animals↗