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T Hofstad

Publications and source records attributed to T Hofstad.

At least 19 recordsLinked to original sources
PubMed2000

Molecular characterization and allelic distribution of the phage-mediated hyaluronidase genes hylP and hylP2 among group A streptococci from western Norway.

Forty-two isolates of group A streptococcus from patients with invasive and non-invasive diseases in western Norway, belonging to the emm sequence types emml, emm3, emm6, emm22, emm28, emm75 and emm78 were screened by PCR for the phage-mediated hyaluronidase genes hylP and hylP2. The amplified genes were characterized by nucleotide sequencing and/or by PCR-RFLP, with the objective of looking for possible associations between alleles of these two genes and invasiveness. The hylP was amplified from all isolates and two main alleles were found hylP-emm3 in all emm3 isolates and hylP-emm6A in all emm6 isolates, the latter possibly generated by an intergenic recombination between hylP and hylP2. The isolates of the other sequence types had either of these two alleles, or both. Only 27 isolates gave amplicons of the appropriate size with the primers targeting hylP2. Sequencing of these amplicons showed two main types: one was similar to the published hylP2 and the other (hylP-emm6B) was probably a variant of hylP. PCR-RFLP revealed the presence of both hylP-emm6B and hylP2 in at least six of the emm6 isolates. The alleles of both hylP and hylP2 seemed to have emm sequence type preferences. No association between invasiveness and specific phage-mediated hyaluronidase genes/alleles or the production of extracellular hyaluronidase was observed.

Alleles↗
PubMed2000

Emm gene polymorphism among temporally clustered group A streptococcal isolates in western Norway.

Nineteen group A streptococcal isolates obtained in western Norway from patients with invasive disease during a period of high morbidity and mortality were examined for clonality and emm gene polymorphism. These isolates belonged to the prevalent serotypes during the outbreak, namely T1, T3 or T6. Restriction fragment length polymorphism and sequencing of the emm genes were used to compare these isolates with 14 isolates of the same serotype but from non-invasive infections. The restriction analysis did not identify specific invasive clones. The emm genes in three of the four T3 isolates from invasive disease had nucleotide substitutions inducing a charge difference in the N-terminal part of the M protein. The 4 T6 isolates had a longer emm amplicon when compared to 15 isolates from superficial infections and also showed nucleotide substitutions that could induce conformational changes in the hypervariable end of the M protein. Restriction analysis of the emm amplicon of the T6 isolates in order to estimate the number of A- and C-repeats is described. The emm gene sequence served as an epidemiological marker within the serotypes T3 and T6, but the significance of the emm polymorphism displayed by the isolates from invasive disease is uncertain at this stage.

Antigens, Bacterial↗
PubMed2000

Dysgonomonas gen. nov. to accommodate Dysgonomonas gadei sp. nov., an organism isolated from a human gall bladder, and Dysgonomonas capnocytophagoides (formerly CDC group DF-3).

Results of a polyphasic taxonomic study on an unknown Gram-negative, facultatively anaerobic, coccobacillus-shaped organism isolated from an infected human gall bladder are presented. Phenotypic and molecular taxonomic studies revealed the organism to be close to, but distinct from, organisms designated CDC (Centers for Disease Control and Prevention) group DF-3. The unknown bacterium was readily distinguished from reference strains of Bacteroides, Prevotella, Porphyromonas and related taxa by 16S rRNA gene sequencing, biochemical tests, analysis of cellular long-chain fatty acids and electrophoretic analysis of whole-cell proteins. Based on the results of the present study, it is proposed that the unknown bacterium be classified in a new genus, Dysgonomonas, as Dysgonomonas gadei sp. nov. (type strain CCUG 42882T = CIP 106420T). In addition, a new species, Dysgonomonas capnocytophagoides sp. nov., is proposed to accommodate strains previously belonging to CDC group DF-3. The type species of the genus Dysgonomonas is Dysgonomonas gadei.

Aged↗
PubMed1999

[Tuberculosis in Bergen 1996].

In 1996, 30 patients with tuberculosis were reported from Haukeland University Hospital to the Norwegian Tuberculosis Registry. Culturing proved 63% with mycobacterium tuberculosis (M. tuberculosis). 13 of the patients, eight adults and five children, all natives, were identified as close relatives or friends (cluster). M. tuberculosis with identical restriction fragment length polymorphism pattern (RFLP) were found in all the adults, indicating that they carried the same bacteria strain. We have compared the clinical findings, bacteriology and treatment among the adults in the cluster with other patients with pulmonary tuberculosis identified the same year at the Department of Thoracic Medicine at Haukeland University Hospital. The patients in the cluster were young adults without any previous chest X-ray changes. The other natives with tuberculosis were older, two showing chest X-ray changes indicating former tuberculosis. No difference was seen in sex, BCG status, tuberculin sensitivity, symptoms, physical findings or chest X-ray between the two groups. In the cluster, four patients proved sputum smear positive, as compared to four in the other group. Spread of infection and new cases of M. tuberculosis with identical RFLP were found only in the cluster. Since RFLP analyses of M. tuberculosis started in Norway in 1993, this cluster in Bergen is the largest cluster observed with identical RFLP pattern.

Adolescent↗
PubMed1998

A mouse model for latent tuberculosis.

The aim of the study was to establish a reproducible murine model for latent tuberculosis. We propose an operational definition of latent murine tuberculosis as a stable Mycobacterium-tuberculosis count in lungs and spleens without clinical signs or obvious histopathological changes in the lungs over a long period of time and without spontaneous reactivation of disease. B6D2F1Bom mice were inoculated with a wide range of Mycobacterium tuberculosis doses intraperitoneally or intravenously and followed for a long period to determine suitable conditions to produce latent infection. No anti-tuberculosis drug treatment was used. Microbiological and histopathological studies were carried out. Corticosterone challenge was used to reactivate the latent infection. Mice infected with 4 x 10(4) and 4 x 10(5) bacilli i.p. were followed up to 107 weeks without spontaneous reactivation. The present model is discussed in comparison with previous latent tuberculosis mouse models as well as the possible mechanisms of shift to stationary phase from multiplying bacilli.

Animals↗
PubMed1998

Septicaemia with Neisseria elongata ssp. nitroreducens in a patient with hypertrophic obstructive cardiomyopathia.

Neisseria elongata ssp. nitroreducens, a commensal of the human upper respiratory tract, is a newly recognized cause of endocarditis. We report the isolation of the organism from blood cultures of a 30-y-old man with hypertrophic obstructive cardiomyopathy. The patient was successfully treated with benzylpenicillin and netilmicin in combination, followed by ceftriaxone and amoxicillin.

Adult↗
PubMed1997

Antibiotic susceptibility of group A streptococci in a national consultant hospital in Dar es Salaam: a four year follow-up.

Seventy one Group A streptococcal strains isolated between 1992 and 1995 at Muhimbili Medical Centre in Dar es Salaam were found to be susceptible to penicillin G and cotrimoxazole. All except two strains, which showed intermediate susceptibility, were susceptible to erythromycin. Sixty five strains (91.5%) were resistant to doxycycline. The findings confirm continuing efficacy of penicillin G, erythromycin and contrimoxazole in treating Group A streptococci (GAS). The low prevalence of GAS with intermediate susceptibility to erythromycin and resistance to doxycycline by a majority of the GAS emphasise the need for regular monitoring of antibiotic susceptibility of GAS.

Drug Resistance, Microbial↗
PubMed1995

Chromosomal restriction endonuclease analysis and ribotyping of Bacteroides fragilis.

We have analysed the restriction fragment length patterns of chromosomal DNA and of ribosomal RNA (rRNA) genes in order to investigate the clonal distribution within Bacteroides fragilis isolates. Eighteen blood culture isolates from 18 patients and 4 faecal isolates from 4 subjects were examined. Chromosomal restriction endonuclease analysis (REA) was performed by separating BamHI-generated DNA fragments using polyacrylamide gel electrophoresis (PAGE). Ribotyping was accomplished by hybridizing EcoRI-treated genomic DNA subjected to conventional REA on agarose to a radiolabelled probe obtained from 16+23S rRNA of E. coli. All 22 isolates could be differentiated by their REA patterns with a varying percentage of similar fragments. Analysis of the rRNA gene patterns displayed heterogeneity, and revealed 14 ribotypes among the 18 blood culture isolates and 3 among the 4 faecal isolates. The predominant ribotype among the clinical isolates was also shared by one faecal isolate. The results suggest that no particular clones are predominantly responsible for systemic infection.

Bacterial Typing Techniques↗
PubMed1994

Utility of newer techniques for classification and identification of pathogenic anaerobic bacteria.

Results of genetic and biochemical analyses have broadened our understanding of taxonomic relationships among groups of anaerobic bacteria and have led to a better understanding of the pathogenesis of infection. Conventional bacteriologic methods are still of prime importance for the detection and identification of anaerobic pathogens. The use of nucleic acid probes has so far been restricted to research laboratories. A polymerase chain reaction-generated probe would be most useful for the rapid detection of toxigenic Clostridium difficile in feces. Probes are needed for detection of periodontopathogenic bacteria in dental plaque. Use of nucleic acid probes may become a useful adjunct to classic methodology in reference and teaching laboratories.

Bacteria, Anaerobic↗
PubMed1994

Small-fragment restriction endonuclease analysis in epidemiological mapping of group A streptococci.

The usefulness of small-fragment restriction endonuclease digest analysis (SF-REA) of group A streptococcal DNA with EcoRI, as a supplement to the more conventional T serotyping, was assessed for epidemiological characterisation. One hundred and thirty-five clinical isolates from 1988-1990 were examined. SF-REA provided characteristic fingerprints of all isolates, whereas eight isolates were non-typable by T serotyping. Generally, there was a striking correlation between the results obtained with the two techniques. Furthermore, SF-REA reliably classified the eight T-non-typable isolates and occasionally revealed subgroups within the T serotypes. In addition, SF-REA was useful for the clarification of discrepancies between serotyping results from two different reference laboratories. No obvious correlation was observed between the DNA fingerprints and the clinical manifestations of infection or the geographical origin of the group A streptococcal isolates. SF-REA is a valuable supplement to T typing in epidemiological studies and frequently appears to be a more efficient tool for strain differentiation.

Bacteremia↗
PubMed1993

Stimulation of B lymphocytes by lipopolysaccharides from anaerobic bacteria.

Lipopolysaccharides (LPSs) from anaerobic gram-negative bacteria, including those of low endotoxic activity that are isolated from Bacteroides, Prevotella, and Porphyromonas are potent inducers of DNA replication and polyclonal immunoglobulin production in murine B lymphocytes. The activation is dose-dependent and T cell-independent. Replication of DNA and production of immunoglobulins were also stimulated by lipid A and by the LPS heteropolysaccharide that were isolated by mild acid hydrolysis of the LPSs of Bacteroides fragilis and Fusobacterium nucleatum. Combinations of LPS, lipid A, and acid-degraded polysaccharide amplified the blastogenic response. Antibodies that react with the polysaccharide part of LPSs isolated from members of the Bacteroidaceae are present in healthy human serum.

Animals↗
PubMed1992

Virulence factors in anaerobic bacteria.

Various surface structures can be expressed in Bacteroides fragilis, but little is known about capsular structures in other non-spore-forming anaerobes. Fimbriae have been isolated from Bacteroides fragilis and Porphyromonas gingivalis. The importance of iron-repressible outer membrane proteins as virulence factors in Bacteroides fragilis is under study. The low endotoxic activity of Bacteroides fragilis lipopolysaccharide can be attributed to the chemical composition of this organism's lipid A. A tissue culture system for the demonstration of Bacteroides fragilis enterotoxin has recently been described. The toxins A and B of Clostridium difficile are immunologically distinct. The importance of IgA proteases and other enzymes as virulence factors in anaerobic bacteria remains unclear.

Animals↗
PubMed1992

DNA base composition, aerotolerance and enzyme patterns of Leptotrichia buccalis.

The guanine plus cytosine content of the DNA of Leptotrichia buccalis varied from 28.4 to 29.5 mol% (three strains). Eleven strains examined grew well under anaerobic and microaerobic conditions, but slowly in air in the presence of CO2. When examined for preformed enzymes in the APIZYM Complete Research Kit, positive reactions were obtained for several glucosidases and carboxylic ester hydrolases, and for a few peptidases.

Air↗
PubMed1991

Synergistic effect on blastogenesis in murine spleen cells of lipopolysaccharide, lipid A, and acid-degraded polysaccharide from Fusobacterium nucleatum.

Interchangeable combinations of Fusobacterium nucleatum Fev1 lipopolysaccharide (LPS) with its split products by acetic acid hydrolysis, i.e. lipid A (LA) and degraded polysaccharide (PS), amplified the blastogenic response in murine spleen cell cultures as measured by [3H]thymidine uptake. Athymic murine spleen cells precultured with LPS-Fev1 for 48 h (stage 1), washed twice and cultured together with fresh cells and either LA or PS for 72 h (stage 2) gave a synergistic response over that found in spleen cell cultures of thymic mice. Spleen cells pre-cultured with LA or PS and with fresh cells and LPS-Fev1 added to stage 2 cultures gave less significant amplification compared with precultures of LPS and either LA or PS together with fresh cells added to stage 2. Precultures with LA, PS or LPS-Fev1 and with pokeweed mitogen (PWM) and fresh cells added produced an additional increment of synergy which was most pronounced in spleen cell cultures of normal mice.

Acetates↗
PubMed1991

Neonatal tetanus despite protective serum antitoxin concentration.

Using the ELISA technique to estimate serum antibodies against tetanus toxin, seven neonates with clinical tetanus were found to have antibody levels 4-13 times higher than the presumed minimum protective level of 0.01 IU/ml. All but one of their mothers had been vaccinated with tetanus toxoid in pregnancy. In two other neonates, whose mothers had received multiple booster doses of toxoid during pregnancy, the anti-toxin concentrations were 100- and 400-times the presumed protective level. Therefore the toxin dose may overwhelm the pre-existing anti-toxin level and produce disease. Furthermore, multiple booster injections of tetanus toxoid may not only enhance serum anti-toxin titres, but could also lead to an ineffective immune response.

Enzyme-Linked Immunosorbent Assay↗
PubMed1991

DNA fingerprinting of isolates of Staphylococcus aureus from newborns and their contacts.

During a study on the epidemiology of Staphylococcus aureus colonization in newborns, mothers, and hospital staff, S. aureus was isolated from 536 of 1,945 specimens. Ninety-three isolates of S. aureus from the three groups of individuals were included in a study to evaluate the potential of DNA fingerprinting for strain differentiation. The 93 isolates were also phage typed and their plasmid profiles were analyzed. Cleavage of DNA with BamHI resulted in 13 different DNA restriction endonuclease band patterns (DNA REBPs), one of which consisted of eight isolates whose DNA was not cleaved with BamHI. The DNAs from these eight isolates were easily cleaved with HindIII. The different DNA REBPs were stable both during in vitro and in vivo growth and allowed strain differentiation within phage groups or types. We could not show any strong association between DNA REBP classes, phage types or groups, and plasmid profiles. Of the 93 isolates, 27 (29.0%) could not be phage typed and 12 (12.9%) lacked plasmids. We therefore conclude that DNA fingerprinting is a powerful tool, in addition to phage typing and plasmid profile analysis, for strain differentiation of S. aureus.

Adult↗