Biomedical subjects

R K Selander

Publications and source records attributed to R K Selander.

At least 73 records · Page 4Linked to original sources

PubMed1990

Genotypic heterogeneity of strains of Citrobacter diversus expressing a 32-kilodalton outer membrane protein associated with neonatal meningitis.

Genetic diversity and relationships among 42 strains of Citrobacter diversus recovered from the cerebrospinal fluid of human infants with meningitis and from other clinical sources in the United States were estimated on the basis of electrophoretically detectable allelic variation in 20 genes encoding metabolic enzymes. Sixteen distinctive multilocus enzyme genotypes were identified, among which the mean genetic diversity per locus was 0.244. The recovery of isolates of the same genotype in several regions of the United States and over periods as long as 20 years indicates that the population structure of C. diversus is clonal. There was little association between multilocus enzyme genotype and biotype, piliation, or presence of a 32-kilodalton outer membrane protein. The observation that the 32-kilodalton outer membrane protein, which is expressed predominantly by strains recovered from infants with meningitis, occurs in a variety of genotypically diverse clones belonging to several phylogenetic lineages supports the hypothesis that this protein confers virulence.

Alleles↗

PubMed1990

Home-cage open-field ambulation after maze learning in mice.

The present paper indicates that it is with appropriate methods, i.e., maze learning and a not-previously used home-cage open-field, possible to observe a learning-induced ambulation increase in a familiar environment lacking novel cues. This finding is at variance with an earlier one achieved by electromagnetic recordings indicating a decrease in activity in the home-cage after passive avoidance conditioning.

Animals↗

PubMed1990

Characteristics of serogroup A Neisseria meningitidis responsible for an epidemic in Ethiopia, 1988-89.

In September 1988, an epidemic of meningococcal disease started in Ethiopia. 21 Neisseria meningitidis isolates recovered from patients in Addis Ababa and towns 200 km south of the capital were characterized by serogrouping, serotyping, testing of susceptibility to antibiotics, restriction endonuclease fingerprinting, and multilocus enzyme electrophoresis. The 21 isolates were essentially homogeneous for all properties tested and belonged to clone III-1 of serogroup A N. meningitidis, which was also responsible for the epidemics in Saudi Arabia in 1987 and in Sudan and Chad in 1988.

Adolescent↗

PubMed1990

Serogroup A Neisseria meningitidis of clone III-1 present in western Norway as early as 1969-73.

A clone of serogroup A Neisseria meningitidis recognized by multilocus enzyme electrophoresis and designated as clone III-1, has caused major epidemics of meningococcal disease in various parts of the world since the 1970s. In Norway, serogroup B meningococci have been responsible for an epidemic since the mid-1970s. We have studied a sample of 53 meningococci isolated from patients in western Norway prior to the serogroup B epidemic. 22/35 meningococcal isolates collected 1969-73 represented clone III-1, whereas this clone was not found in the 18 isolates from 1962-68. It has been speculated that the epidemic of meningococcal disease in Finland caused by clone III-1 in 1973-75 had spread from an epidemic in USSR that began in 1969. Our findings demonstrate, however, that the clone III-1 was present in Scandinavia in 1969.

Clone Cells↗

PubMed1989

Genetic characterization of clones of the bacterium Listeria monocytogenes causing epidemic disease.

One hundred and seventy-five isolates of the pathogenic bacterium Listeria monocytogenes recovered from human clinical (blood and cerebrospinal fluid), animal, and environmental sources in Europe, North America, and elsewhere were analyzed electrophoretically for allelic variation at 16 genetic loci encoding metabolic enzymes. Forty-five distinctive allele profiles (electrophoretic types, ETs) were distinguished, among which mean genetic diversity per locus (H) was 0.424. Cluster analysis of a matrix of genetic distances between paired ETs revealed two primary phylogenetic divisions of the species separated at a distance of 0.54. ETs in division I were presented by strains of serotypes 4b, 1/2b, and 4a, whereas strains of ETs in division II were of serotypes 1/2a and 1/2c. Human and animal isolates did not represent distinctive subsets of ETs. The occurrence of linkage disequilibrium between enzyme loci and the widespread distribution of certain ETs indicate that the genetic structure of L. monocytogenes is clonal. One clone, marked by ET1, caused major epidemics of human disease in western Switzerland in the period 1983-1987 and in Los Angeles County, California, in 1985, both of which were attributed to contamination of soft cheese. ET 1 is closely related to the clone (ET7) that caused two large outbreaks of listeriosis in Massachusetts in 1979 and 1983.

Bacteriophage Typing↗

PubMed1989

Identification of a high-virulence clone of type III Streptococcus agalactiae (group B Streptococcus) causing invasive neonatal disease.

Chromosomal genotypes of 128 isolates of six serotypes (Ia, Ib, Ic, II, Ic/II, and III) of Streptococcus agalactiae (group B Streptococcus) recovered predominantly from human infants in the United States were characterized by an analysis of electrophoretically demonstrable allelic profiles at 11 metabolic enzyme loci. Nineteen distinctive electrophoretic types (ETs), representing multilocus clonal genotypes, were identified. Mean genetic diversity per locus among ETs of isolates of the same serotype was, on average, nearly equal to that in all 19 ETs. Cluster analysis of the ETs revealed two primary phylogenetic divisions at a genetic distance of 0.65. A single clone (ET 1) represented by 40 isolates expressing type III antigen formed division I. Division II was composed of 18 ETs in three major lineages diverging from one another at distances greater than 0.35 and included strains of all six antigenic classes. The type III organisms in division I produce more extracellular neuraminidase and apparently are more virulent than the type III strains in division II, which are related to strains of other serotypes that cause disease much less frequently. The existence of this unusually virulent clone accounts, in major part, for the high morbidity and mortality associated with infection by type III organisms.

Genotype↗

PubMed1989

Diversity and sources of rapidly growing mycobacteria associated with infections following cardiac surgery.

Eighty-nine isolates of rapidly growing mycobacteria associated with cardiac bypass-related infections were characterized. Isolates from sporadic infections belonged to eight taxonomic groups and displayed numerous multilocus enzyme genotypes, plasmid profiles, and heavy metal and antibiotic resistance patterns. Compared with 449 noncardiac wound isolates, 45 sporadic cardiac isolates were more likely to be Mycobacterium fortuitum and M. smegmatis and less likely to be M. chelonae. About 80% of cardiac and noncardiac isolates were from southern coastal states. Eight outbreaks of cardiac bypass-related infections were identified. Strains from each outbreak were genotypically distinctive, and five outbreaks involved more than one strain. In two outbreaks, isolates from environmental sources and noncardiac infections were similar or identical to isolates from sternal wound infections. The heterogeneity of these isolates suggests that most isolates are unrelated and are derived from local environmental sources rather than from contaminated commercial surgical materials or devices.

Cardiopulmonary Bypass↗

PubMed1989

Host and bacterial factors associated with Haemophilus influenzae type b disease in Minnesota children vaccinated with type b polysaccharide vaccine.

Host and bacterial factors were evaluated among 86 Minnesota children with Haemophilus influenzae type b disease detected by active surveillance after introduction of type b polysaccharide vaccine in the state. Children were 2-6 y of age. Thirty-three (38%) had been vaccinated. There was no significant difference between the frequency of low serum concentrations of IgM, IgA, IgG, or IgG2 in the vaccinated and nonvaccinated subjects (13% vs. 8%, P = .5). The presence of the Gm immunoglobulin allotype phenotype (1,3,17;23;5,13,21), previously associated with a lower relative risk of vaccine failure in children from other states, was associated with a fourfold decrease in the relative risk of vaccine failure in Minnesota (P less than .07). Haemophilus isolates from 58 of the children were available for clonal characterization by multilocus electrophoresis and outer membrane protein subtyping. There were no significant differences between the clone distribution of the strains causing disease in vaccinated and nonvaccinated patients, and nearly all disease-producing clones in Minnesota also are known to cause disease in other areas of the country. Thus, vaccine failure in Minnesota is infrequently associated with hypogammaglobulinemia or with infection by unusual clones of a H. influenzae type b. Also, the Gm phenotype associated with protection against vaccine failure in other areas of the USA appears to be protective in Minnesota.

Antibodies, Bacterial↗

PubMed1989

Bacteriologic epidemiology of Hemophilus influenzae type b strains causing invasive infections in Finland.

Consecutive Hemophilus influenzae type b (Hib) isolates (333 total) from children with invasive disease in Finland in 1985-1986 were analyzed. All belonged to the common genetic clusters described in the USA and Europe. However, detailed typing demonstrated some characteristics unique to Hib strains in Finland. Of the isolates, 86% belonged to one of four distinct patterns according to the combination of outer membrane protein subtype, biotype, and lipopolysaccharide serotype: 1-I-1 (25%), 1-II-9 (8%), and 1c-I-1 (18%). Pattern 1-II-9 has not been previously reported; it was most commonly found in the most densely populated area of Finland and among children cared for outside the home. Multilocus enzyme electrophoresis revealed that 87% of isolates with the pattern 1c-I-1 belonged to the electrophoretic type 21.8, which is seldom recovered from patients with invasive Hib disease in other countries.

Adolescent↗

PubMed1989

Clonal analysis of Hemophilus influenzae isolated from children from Pakistan with lower respiratory tract infections.

The clonal diversity of 105 Hemophilus isolates from the blood of children with lower respiratory tract infection in Pakistan was analyzed. Ten isolates were identified as H. parainfluenzae and 95 as H. influenzae. Of the H. influenzae isolates, 61 (64%) were serotype b and 34 (36%) were nontypable; 95% of the type b isolates were members of a single clonal group (as defined by multilocus enzyme electrophoresis, SDS-PAGE outer membrane protein profile, and biotype). This clone is rarely observed among type b strains recovered from patients with invasive type b disease in the USA or Europe. The nontypable isolates in Islamabad also were clonally restricted: 9 clonal groups were found among 34 isolates, with just 5 clonal groups accounting for most (82%) of the strains. Children infected with type b strains were hospitalized more often than those with nontypable H. influenzae disease (64% vs. 41%, P = .06), but no other clinical or demographic features distinguished children infected by type b and nontypable strains.

Bacterial Outer Membrane Proteins↗

PubMed1989

The epidemiology of Pseudomonas aeruginosa in oncology patients in a general hospital.

Pseudomonas aeruginosa colonization and infection was studied over a 6-mo period in a 36-bed mixed general medical-oncology unit. We used selective media for serial surveillance cultures on 283 patients, the environment, and personnel. Twelve percent of patients were colonized on admission and 10% acquired P. aeruginosa. Using serotyping and multilocus enzyme electrophoresis, we identified 63 genetically distinctive strains; four prevalent strains accounted for 21% of isolates. Only 5 of 33 nosocomial acquisitions were due to horizontal transmission. Nine acquisitions were linked to environmental sources (e.g., sink surfaces), which often harbored antibiotic-resistant strains but posed a risk only to oncology patients. Although significant Pseudomonas infections occurred in only 11% of colonized patients, 63% of colonized severely neutropenic patients--predominantly those who had acquired the prevalent, often environmentally linked strains--developed infections. Thus, P. aeruginosa was a significant pathogen in oncology patients; typing by multilocus enzyme electrophoresis allowed the detection of important environmental sources.

Female↗

PubMed1989

Genetic diversity of penicillin G-resistant Neisseria meningitidis from Spain.

Genotypic and phenotypic diversity among 16 penicillin G-resistant (Penr) isolates of Neisseria meningitidis recovered from human blood or cerebrospinal fluid in Spain was compared with that among 12 penicillin-susceptible (Pens) isolates by the use of multilocus enzyme electrophoresis, serotyping, auxotroph testing in chemically defined media, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis of penicillin-binding proteins (PBPs). Thirteen distinctive multilocus enzyme genotypes (electrophoretic types [ETs] ) were identified among the 28 isolates. There was slightly less genetic diversity among the eight ETs of Penr isolates (H = 0.385) than among the eight ETs of Pens isolates (H = 0.431). Cluster analysis demonstrated two distinctive complexes of ETs and one ET that was not closely related to either complex. The possibility of a singular clonal origin of penicillin G-resistant isolates was excluded by the observations that resistance occurred in isolates of each of the two distantly related complexes of ETs, that three of the four ETs represented by multiple isolates included both susceptible and resistant strains, and that serotypes and growth requirements were not associated with the resistance phenotype. The 28 isolates showed a relatively homogeneous pattern of four PBPs, with apparently reduced penicillin G binding by PBP 3 of the Penr isolates.

Bacterial Proteins↗

PubMed1989

Typing of urogenital, maternal, and neonatal isolates of Haemophilus influenzae and Haemophilus parainfluenzae in correlation with clinical source of isolation and evidence for a genital specificity of H. influenzae biotype IV.

Over a period of 6 years, 114 strains of Haemophilus influenzae and Haemophilus parainfluenzae were isolated from genital, mother-infant, or neonatal infections. Their serotypes, biotypes, antibiotic resistance phenotypes, and outer membrane protein (OMP) electrophoretic patterns were characterized and correlated with the various clinical outcomes. Genital H. influenzae and H. parainfluenzae appeared to behave mostly as opportunistic pathogens; for instance, 62% of the cases of endometritis or pelvic inflammatory disease were related to the presence of an intrauterine device. However, as seen clearly in one case, the strains may be sexually transmitted. The analysis of OMP patterns proved to be a very convenient method to seek evidence for the sexual origin of the infection. H. influenzae was more often involved in complicated genital infections than was H. parainfluenzae. Nontypeable and biotype II H. influenzae strains were the more frequent isolates, except in pelvic inflammatory diseases, in which biotype I prevailed, and in mother-infant infections, in which one-fourth of the cases were due to biotype IV. Characterization of H. influenzae isolates did not support a general concept of specific genital strains. However, strains of biotype IV clearly stood out with two characteristics: (i) a peritrichous fimbriation and (ii) a very peculiar homogeneous OMP pattern comprising an OMP of molecular weight approximately 18,000 unique to this biotype. These characteristics were also found in H. influenzae biotype IV strains isolated from genital infections in the United States and used as controls. H. influenzae biotype IV strains may thus correspond to a group somewhat adapted to the genital tract.

Female↗

PubMed1989

Clonal diversity and relationships among strains of Yersinia enterocolitica.

Allelic variation in the chromosomal genome of 81 isolates of Yersinia enterocolitica and single isolates of Yersinia intermedia, Yersinia frederiksenii, Yersinia mollaretii, and Yersinia kristensenii was assessed by analysis of electrophoretically demonstrable polymorphism in 21 genes encoding metabolic enzymes. Eighteen distinctive multilocus genotypes (electrophoretic types [ETs]) were identified. Clustering of the ETs from a matrix of pairwise genetic distances, based on the 21 enzyme loci, confirmed the genetic distinctness of serogroup 3 isolates of Y. intermedia, Y. frederiksenii, Y. mollaretii, and Y. kristensenii and identified another serogroup 3 isolate that was also not a member of Y. enterocolitica. The 13 ETs of Y. enterocolitica clustered into two groups: cluster A, which included eight ETs represented by isolates of serogroups 1; 2; 3; 5,27; and 9, and cluster B, which included four ETs represented by isolates of serogroups 8, 13, and 21. Clones of cluster A were found to be distributed worldwide, but those of cluster B were largely restricted to North America. Isolates of genotypes belonging to cluster B were lethal to mice, whereas those of cluster A were not, suggesting an influence of the chromosomal background on the virulence of Y. enterocolitica.

Alleles↗

PubMed1989

Sulfonamide resistance in Neisseria meningitidis isolates of clones of the ET-5 complex.

A distinctive group of genetically closely related clones, as determined by multilocus enzyme electrophoresis, the ET-5 complex, has been responsible for an epidemic of meningococcal disease in Norway since the mid-1970's. Most isolates of the ET-5 complex from Norway are sulfonamide-resistant, serogroup B, and serotype 15:P1.16. Clones of the ET-5 complex that have been identified as the causative agents of recent outbreaks and epidemics in many other parts of the world show, outside Northern Europe, different associations of serotype protein antigens. We here report the analysis of sulfonamide susceptibility of isolates of the ET-5 complex from various geographic sources. There was no difference in resistance according to geographic source, serogroup, or serotype of the isolates, demonstrating that, in contrast to serotype and serogroup, sulfonamide resistance is an essentially invariant property of clones of the ET-5 complex.

Drug Resistance, Microbial↗

PubMed1988

Evolutionary genetics of the encapsulated strains of Haemophilus influenzae.

Genetic relationships among 2209 isolates of Haemophilus influenzae of polysaccharide capsule serotypes a, b, c, d, e, and f were determined by analyzing electrophoretically demonstrable allelic variation at 17 chromosomal enzyme loci. We distinguished 280 electrophoretic types (ETs), representing distinctive multilocus genotypes. Genetic diversity among ETs of isolates of the same serotype was, on average, only 67% of that in the total sample, and no ETs were shared among isolates of different serotypes. Cluster analysis of the ETs revealed 2 primary phylogenetic divisions at a genetic distance of 0.66 and 12 major lineages diverging from one another at distances greater than 0.42. In general, strains of different phylogenetic lines or groups of allied lineages have characteristic cap region restriction fragment length polymorphism patterns obtained by digestion of genomic DNA with EcoRI. Strains producing serotype c, e, and f capsules have no close relationships to those of other encapsulated strains. Lineages of both serotype a and b strains occur in each primary phylogenetic division, most probably as a result of the transfer of serotype-specific sequences of the cap region between clonal lineages. Serotype a strains allied in division I with a group of abundant serotype b clones and the serotype d strains apparently are more virulent than the serotype a strains in division II, which are related to serotype b and f strains that rarely cause invasive disease.

Alleles↗

PubMed1988

Genetic diversity and relationships of two pathovars of Pseudomonas syringae.

To determine genetic relationships within and between two pathovars of Pseudomonas syringae, strains typical of P. syringae pv. tomato (P. s. tomato) and selected strains of P. syringae pv. syringae (P. s. syringae) were characterized by three methods. DNA-DNA hybridization experiments showed that strains of P. s. tomato and P. s. syringae were, respectively, 86-100% and 37-47% homologous to DNA from a P. s. tomato reference strain when tested under stringent conditions. An analysis of electrophoretic variation in enzymes encoded by 26 loci placed 17 P. s. tomato strains studied in a group of four electrophoretic types, and these strains had a mean genetic diversity per locus of 0.076. Six P. s. syringae strains formed a second group of six electrophoretic types, which had a higher mean genetic diversity per locus of 0.479. The mean genetic distance separating P. s. tomato from P. s. syringae (D = 0.94) was unexpectedly large for strains of a single species. An analysis of restriction fragment length polymorphisms (RFLPs) with three cloned hybridization probes demonstrated that each of the P. s. tomato and P. s. syringae strains was unique. A method was developed to quantify the RFLP difference between pairs of strains, and cluster analysis revealed relationships among P. s. tomato, but not among P. s. syringae, that were similar to those based on enzyme polymorphisms. Implications of these findings for bacterial systematics and epidemiology are discussed.

Electrophoresis↗

PubMed1988

Genetic diversity and relationships among isolates of Rhizobium leguminosarum biovar phaseoli.

Fifty-one isolates of Rhizobium leguminosarum biovar phaseoli from various geographic and ecological sources, largely in Mexico, were characterized by the electrophoretic mobilities of 15 metabolic enzymes, and 46 distinctive multilocus genotypes (electrophoretic types [ETs]) were distinguished on the basis of allele profiles at the enzyme loci. Mean genetic diversity per enzyme locus among the 46 ETs was 0.691, the highest value yet recorded for any species of bacterium. The occurrence of strong nonrandom associations of alleles over loci suggested a basically clonal population structure, reflecting infrequent recombination of chromosomal genes. Multilocus genotypic diversity was unusually high, with the most strongly differentiated pairs of ETs having distinctive alleles at all 15 loci and major clusters of ETs diverging at genetic distances as large as 0.89. This great diversity in the chromosomal genome raises the possibility that R. leguminosarum biovar phaseoli is a polyphyletic assemblage of strains. As other workers have suggested, the inclusion of all strains capable of nodulating beans in a single biovar or species is genetically unrealistic and taxonomically misleading. A biologically meaningful classification of Rhizobium spp. should be based on assessment of variation in the chromosomal genome rather than on phenotypic characters, especially those mediated for the most part or wholly by plasmid-borne genes, such as host relationships.

Alleles↗