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Biomedical subjects

H Miörner

Publications and source records attributed to H Miörner.

53 records · Page 3Linked to original sources
PubMed1989

In vitro activities of cefcanel and some other cephalosporins against Pasteurella multocida.

Thirty-five strains of Pasteurella multocida from humans and animals were tested for susceptibility to five cephalosporins by a broth dilution method. Cefcanel showed high activity against all isolates (MIC and MBC, less than or equal to 0.64 micrograms/ml). The corresponding figure for cefaclor and cefuroxime was 2.56 micrograms/ml. Cefadroxil and cephalexin were the least active compounds tested.

Animals↗
PubMed1988

Improved isolation of mycobacteria other than Mycobacterium tuberculosis on isoniazid-containing Löwenstein-Jensen medium.

The benefit of including isoniazid-containing Löwenstein-Jensen medium for primary isolation of mycobacteria was evaluated in 3,726 clinical specimens. This media increased the primary isolation of mycobacteria other than Mycobacterium tuberculosis by 9.2%, facilitated macroscopical reading and aided presumptive identification of the isolated mycobacteria.

Culture Media↗
PubMed1985

Variations in binding of mammalian fibrinogens to streptococci groups A, B, C, E, G and to Staphylococcus aureus.

Twenty-eight beta-hemolytic streptococci of groups A, B, E, G and Streptococcus equisimilis as well as four Staphylococcus aureus strains were tested for their ability to bind fibrinogen preparations from different animal species: homo, baboon, rabbit, rat, guinea-pig, dog, horse, pig, cow and sheep. The patterns of binding indicated differences in the structures of the bacterial fibrinogen receptors. There were higher binding levels in streptococci groups A, G, and S. equisimilis than in representative group B and E strains. Considerable differences in the binding capacity were found within streptococci groups A and E. Group C and group G strains showed rather similar patterns and could be further divided into high-level and low-level binding strains. There is no correlation between binding levels of different animal fibrinogen preparations and the strains isolated from corresponding animals. Recent studies by others have shown that resistance to phagocytosis is mediated by fibrinogen-binding in streptococci group A. The existence of similar fibrinogen-binding structures in several streptococcal species indicates an important role with a definite survival value. It also suggests that M or T protein analogues are present in streptococci groups C, G and E.

Animals↗
PubMed1984

Assay of type-specific M antigens on whole group A streptococci.

A novel radioimmunoassay of type-specific M antigens on whole group A streptococcal cells is described. Absorbed rabbit anti-M antisera directed against M types 12 and 49 were used for determining M antigens on intact bacterial organisms. Staphylococcal protein A labelled with 125I was used as an anti-antibody reagent. The absorbed antisera were tested against ten homologous and 48 heterologous serotypes. All homologous serotypes gave an unequivocal reaction distinct from the weaker reaction with the heterologous serotypes. The type-specificity of the reaction was confirmed by the removal of type-specific antibodies after absorption to purified M protein coupled to Sepharose 4B. The results indicate that the described method is a simple and reliable technique for the recognition of M types of group A streptococci and offers a valuable tool for studies of M antigen in situ.

Animals↗
PubMed1984

On the interaction between beta 2-microglobulin and group A streptococci.

beta 2-microglobulin (beta 2m) was found to interact with many group A streptococcal strains. The interaction appeared to require multipoint attachment, since monomeric beta 2m in solution showed no binding, whereas both beta 2m monomers bound to liposomes, and beta 2m in aggregates showed affinity for the bacteria. Aggregated HLA antigens (-A, -B and -C) and aggregated beta 2m exhibited the same binding patterns when tested in binding experiments with various group A streptococcal strains. Furthermore, beta 2m aggregates in excess completely blocked the binding of aggregated HLA antigens, thereby demonstrating that beta 2m is able to interact with streptococcal surface structures also when it is part of the HLA antigen complex. M protein-positive group A streptococcal strains bound significantly more beta 2m than M protein-negative variants of these strains. Purified M 12 protein partly inhibited the binding of radiolabelled beta 2m aggregates to whole streptococci, and in gel filtration and affinity chromatography experiments, the M 12 protein interacted with beta 2m. These various data suggest that the interaction between beta 2m and group A streptococci could be mediated by M protein. Lipoteichoic acid (LTA) is a constituent of the streptococcal cell wall that has been reported to form complexes with M protein at the bacterial cell surface. However, LTA did not influence the interaction between beta 2m and streptococci, suggesting that the binding of beta 2m to streptococcal M protein represents a pure protein-protein interaction. In vivo such an interaction could be established between infecting streptococci and host cells. Among 45 strains of different M types large differences in beta 2m binding were recorded, whereas among 60 strains of the classical nephritogenic M types 12 and 49, all were highly beta 2m-reactive, which points towards a role for beta 2m in streptococcal pathogenicity.

Bacterial Proteins↗
PubMed1984

Surface characteristics of group A streptococci with and without M-protein.

Twenty M protein-positive and eight M protein-negative strains of group A streptococci were investigated with respect to surface hydrophobicity and amount of lipoteichoic acid (LTA). Surface hydrophobicity as determined in polymer two-phase systems varied substantially between individual strains and there was no correlation to the presence of antiphagocytic M protein. The amount of LTA on the surface of the bacteria varied with hydrophobic affinity of the cells. Strains with a high content of surface LTA were found among both M-positive and M-negative streptococci. Cellular and extracellular LTA was estimated on six strains by the ability of hot phenol extracts and culture fluids to sensitize erythrocytes and by rocket immunoelectrophoretic quantitation. Differences in content of surface LTA did not correlate to differences in the total amount of cellular LTA. Pepsin digestion of M-positive group A streptococci at suboptimal pH resulted in a loss of M antigen whereas surface LTA and the hydrophobic interaction liability was retained. The results indicate that the degree of surface hydrophobicity as measured by two-phase partitioning is not correlated to either the type-specific or the antiphagocytic moiety of M protein. The results support the correlation between surface LTA and surface hydrophobicity of group A streptococci.

Antigens, Bacterial↗
PubMed1983

Lipoteichoic acid is the major cell wall component responsible for surface hydrophobicity of group A streptococci.

The contribution of lipoteichoic acid (LTA) to the hydrophobic surface properties of group A streptococci was investigated in aqueous dextran-polyethylene glycol two-phase systems. Enzymatic digestions were performed to characterize the hydrophobic surface structure. The results obtained indicated that LTA is a major factor responsible for the hydrophobic character of the cell surface of group A streptococci. This was further supported by the similarity of partition in polymer two-phase systems between whole group A streptococci and tritiated LTA extracted from a group A streptococcal strain. Surface LTA was also determined on intact organisms by a new method measuring the adsorption of antibodies to LTA to the bacterial surface. A correlation was found between the content of surface LTA and the hydrophobicity of the group A streptococci. We conclude that surface-associated LTA is the major factor determining surface hydrophobicity of group A streptococci.

Antigens, Bacterial↗
PubMed1982

Isoelectric points and surface hydrophobicity of Gram-positive cocci as determined by cross-partition and hydrophobic affinity partition in aqueous two-phase systems.

Thirty-nine streptococcal strains belonging to groups A, C, and G and 12 staphylococcal strains were investigated with respect to surface charge and hydrophobicity. Isoelectric points of the bacteria were determined by cross-partition experiments in dextran-polyethylene glycol two-phase systems containing charged polymers. The results obtained indicate that group A, C, and G streptococci have isoelectric points of pH 3.75 +/- 0.15 standard deviation. Staphylococci show an isoelectric point of around pH 2 and thereby differ markedly from the streptococci. Pretreatment of bacteria with human serum resulted in a significant change in the isoelectric points of streptococci. In a second series of experiments, an aqueous dextran-polyethylene glycol two-phase system containing polyethylene glycol palmitate or stearate was used to study the hydrophobic surface properties of the bacterial cells. The partition of the staphylococci was not influenced by the addition of up to 1% (wt/wt) polyethylene glycol palmitate or stearate, whereas the streptococci showed a large variation in affinity for polyethylene glycol-bound hydrophobic groups. The bacterial strains included in the study were also tested for uptake of human serum proteins. A positive correlation was found between the hydrophobic affinity of group A streptococci and the density of receptors for aggregated beta-2-microglobulin.

Blood↗
PubMed1980

Effect of specific binding of human albumin, fibrinogen, and immunoglobulin G on surface characteristics of bacterial strains as revealed by partition experiments in polymer phase systems.

Four strains of gram-positive cocci with different combinations of positive binding of human proteins were investigated with respect to changes in physicochemical surface properties after specific protein binding. Staphylococcus aureus Cowan I, two group A beta-hemolytic streptococci, and one group G streptococcal strain were studied; they represented three different combinations of reactivity for human serum albumin, human immunoglobulin G, and fibrinogen. Using single-tube partition of bacterial cells in a dextran-polyethylene glycol system of constant polymer concentration but varying ionic compositions, it was possible to detect changes in the partition of bacteria after specific protein binding. There was a correlation between the binding of radiolabled human proteins to the bacterial strains and the effect of human proteins on the partition of the bacteria in the phase systems. Thus, the specific binding of proteins to the bacteria changes their physicochemical surface properties. These types of bacteria-protein interactions may play an important role in modulating host-parasite relationships.

Animals↗
PubMed1980

High isolation rate of Branhamella catarrhalis from the nasopharynx in adults with acute laryngitis.

Branhamella catarrhalis was isolated from the nasopharynx in 55% of 40 noncompromised adult patients suffering from acute laryngitis. Diplococcus pneumoniae and haemophilus influenzae were found in another 5 and 8%, respectively; one patient had group A streptococci in the throat specimen. In 90% of the patients the laryngitis complaints were preceded by symptoms of an acute respiratory tract infection. Two of the patients with B. catarrhalis showed a significant titre conversion against influenza B and parainfluenza type e virus, respectively. Attempts to isolate virus failed in all cases. The results indicate that B. catarrhalis, known to cause acute otitis media in small children and respiratory tract infections in adult compromised hosts, may be involved in the etiology of acute laryngitis in otherwise healthy adults.

Acute Disease↗
PubMed1979

Effects of leukocyte and fibroblast interferon on events in the fibroblast cell cycle.

Serum-depleted human foetal skin fibroblasts were stimulated by addition of 10% foetal calf serum to proliferate synchronously for at least one cell cycle. This proliferation was suppressed by leukocyte or fibroblast interferon (IF), which prolonged the G1 phase and diminished the rate of DNA synthesis during the S phase in a dose-dependent manner. When used in identical concentration, as judged in terms of units of antiviral activity, fibroblast IF had more pronounced effects on cell cycle events than leukocyte IF. Interferon exerted its effect in early G1, before the cells were irreversibly committed to DNA synthesis.

Cell Cycle↗
PubMed1978

Modulation of immune responses in newborn and adult mice by interferon.

Interferon was found to have both suppressive and enhancing effects on the antibody response in newborn and adult mice. Evidence was obtained that these effects are primarily evoked during the initial steps controlling cell proliferation. Stimulation of thymus and spleen cells with a T-cell mitogen was enhanced by low doses and suppressed by high doses of interferon. Treatment of parental spleen cells with interferon before injecting them into immunized F1 hybrid mice resulted in an enhanced allogeneic effect. These results are compatible with the hypothesis that interferon affects T cells and has an immunoregulatory role, either by inhibiting the action of suppressor cells or by promoting immunological maturation.

Animals↗
PubMed1978

Interferon production in glia and glioma cell lines.

Interferon (IF) was produced in glia and glioma cell lines in titers comparable to those produced by human fibroblasts. It was inducible by both Sendai virus and polyriboinosinic:polyribocytidylic acid. "Superinduction" resulted in up to 500-fold-higher titers of IF. The IF appeared to be of the fibroblast type, as revealed by experiments using heat treatment, assay of antiviral activity in heterologous cell lines, and neutralization with specific antisera. Since large amounts of IF may easily be produced with glioma cell lines, such cells may be suitable for mass production of IF.

Cell Line↗
PubMedDate not supplied

Improved microscopical diagnosis of pulmonary tuberculosis in developing countries.

The diagnosis of pulmonary tuberculosis (TB) relies on the bacteriological examination of sputum. However, microscopy of smears made directly from sputum has a low sensitivity and there is an urgent need for improved methods. We have compared microscopy of smears made directly from sputum with microscopy after liquefaction of sputum with household bleach (NaOCl) and concentration of bacteria by centrifugation. In 3 studies performed in Ethiopia and India, the use of the NaOCl method increased the number of samples positive for acid-fast bacilli by more than 100%. The technique is appropriate for developing countries and its application would increase the efficiency of TB control programmes. As a potent disinfectant, NaOCl also has the advantage of lowering the risk of laboratory infection.

Bacteriological Techniques↗