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Biomedical subjects

H Hof

Publications and source records attributed to H Hof.

At least 109 records · Page 6Linked to original sources
PubMed1991

Toxoplasma encephalitis of immunocompetent and nude mice: immunohistochemical characterisation of Toxoplasma antigen, infiltrates and major histocompatibility complex gene products.

The experimental infection of immunocompetent and immunodeficient athymic mice with an avirulent encephalitogenic Toxoplasma strain (DX strain) was employed to study the ensuing encephalitic process by use of histological and immunocytochemical methods. In the acute phase of the infection Toxoplasma cysts and tachyzoites were accompanied by an infiltrate composed of macrophages, CD4+ and CD8+ T cells. In the chronic stage a granulomatous encephalitis developed. In contrast to immunocompetent NMRI mice, athymic nude NMRI mice died 3 weeks post-infection because of a generalized toxoplasmosis with predominant involvement of the brain. A salient feature of murine Toxoplasma encephalitis was up-regulation of class I and II major histocompatibility complex (MHC) gene products. Class I antigen was widely expressed on microglial cells and astrocytes. Class II antigen was only expressed on microglial cells despite a considerable astrogliosis. Our results indicate a differential expression of MHC-determined antigens on brain cells in acute and chronic murine Toxoplasma encephalitis.

Animals↗
PubMed1991

[Incidence of congenital infections].

The discussions on the pros and cons of obstetric screening for connatal infections have been going on for years. We, therefore, conducted a prevalence study of the most common connatal infections. HIV infection, rubella and syphilis were not subjects of this study. We analysed the relevance of these infections in 512 pregnant women and their newborn infants at the moment of delivery. Further serological tests were run three months post partum, if necessary even for a longer period. Cytomegaly IgG antibodies were found in 46% of the examined women, IgM antibodies in 1.3%. Women under the age of twenty and women of low social standing showed the highest rate of prevalence of infection with CMV. The prevalence of IgG antibodies against parvovirus B 19 was 29%. In 10 mothers, positive IgM titers were found at the time of delivery. In all these women, pregnancies had been uneventful. However, 9 mothers exhibited a significantly raised abortion rate within the last 20 months before delivery. 7 of 512 women turned out to be HBs antigen carriers, 3 women and their babies were anti-HCV positive. The prevalence of toxoplasmosis IgG antibodies was 36%, of IgM antibodies 5.3%. By further investigation (Toxo ISAGA, Toxo IgA) we were able to detect one child with connatal toxoplasmosis. We conclude, that screening for parvovirus B 19 and hepatitis C is required only, if there are contact or clinical hints that the patients might have acquired either one of these infections. But we postulate, that a routine screening programme for hepatitis B and toxoplasmosis should be carried out in all pregnant women.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

[Bases of the antibacterial effect of beta lactam antibiotics].

The primary antibacterial effect of betalactam antibiotics is due to the inhibition of cell-wall synthesis. Prerequisites for good antibacterial activity of such an antibiotic are --rapid penetration across the bacterial cell wall, --strong binding to the proper targets in the cytoplasmic membrane, i.e. the penicillin-binding proteins, --resistance to betalactamases which may be produced by the bacterial cell.

Anti-Bacterial Agents↗
PubMed1991

[Bacterial spondylitis caused by Haemophilus aphrophilus].

Four weeks after a slight scratch a 43-year-old man noted a severe back pain. Physical examination gave suspicion of a bacterial spondylitis. From the biopsy of the involved vertebral body Haemophilus aphrophilus was isolated under aerobic growth conditions.

Adult↗
PubMed1990

Treatment of experimental listeriosis by CI 934, a new quinolone.

CI 934, a new quinolone, is only marginally more active in vitro against Listeria monocytogenes and other Listeria spp. than ciprofloxacin. A bactericidal effect is seen only after several hours of incubation. However, mice infected with a virulent strain of L. monocytogenes were protected by parenteral treatment with CI 934. With a dosage of 2 x 2 mg CI 934 per day for three days almost complete remission could be achieved. These results are somewhat better than those obtained in previous experiments with other antibiotics.

4-Quinolones↗
PubMed1990

[Listeria--a challenge for diagnosis].

The isolation of Listeria spp. from polymicrobially contaminated materials from the environment of human beings is rather difficult. Suppression of the concomitant bacterial flora requires selective growth conditions. Different recipes have been reported to achieve this goal, whereby various antibiotics, among which cephalosporins and nalidixic acid, and dyes, such as acriflavin, have been proposed as supplements to suppress gram-positive as well as gram-negative bacteria. Cycloheximide may help to stop the growth of molds. The diversity of recommendations indicates, however, that an optimal selective medium has not yet been found. A possibility for selective enrichment is the cultivation in the cold, i.e. at +4 degrees C. In the future, genetic as well as immunologic methods will ameliorate the detection of Listeria spp. in environmental specimen. Actually, the offered test assays are still too insensitive so that they need a preceding enrichment process. The isolation of Listeria spp. from specimen of patients when they are present in pure culture is rather easy since these bacteria are not fastidious, so that they grow on the commonly used culture media. Sometimes it is difficult to differentiate Listeria spp. from other gram-positive rods. For the sake of the evaluation of a cultural result it is advisable to characterize further the isolate by simple biochemical tests, since the seven known Listeria spp. among the genus Listeria differ quite definitely from each other in respect to their pathogenic potency. Only bacteria belonging to Listeria monocytogenes represent a potential risk for human health.

Animals↗
PubMed1989

Antibacterial activities of the antiparasitic drugs nifurtimox and benznidazole.

Both nifurtimox and benznidazole, which are used for the treatment of Chagas' disease, also display marked antibacterial activities. Characteristically for nitroheterocyclic compounds, they are much more active against anaerobic and microaerophilic bacteria than against aerobic bacteria. Nitroreductase-deficient aerobes are completely resistant, whereas SOS-repair-deficient strains are moderately susceptible. Those strains are rapidly killed.

Bacteria↗
PubMed1989

[The mutagenicity of organic microcontamination in the environment. III. The mutagenicity of selected herbicides and insecticides in the SOS chromotest].

To determine the mutagenicity of selected herbicides and insecticides we examined 26 pure pesticide substances (polychlorinated alicyclic hydrocarbons, phenoxy fatty acids, triazines) with the help of SOS-Chromotest. We used Escherichia coli strain PQ37 in these tests without and with metabolic activation with Aroclor 1254 induced rat liver microsome fraction. None of the substances showed a provable induction of the E. coli-SOS-system, because a great number of the pesticides showed toxic effects against bacteria in high concentrations.

Animals↗
PubMed1988

Histomorphology of experimental listeriosis.

This paper is a survey of the histomorphology of experimental listeriosis based on cooperative studies performed within the past ten years. The influence of various parameters of the infectious agent (pathogenic Listeria monocytogenes serovar 4b, nonpathogenic Listeria innocua serovar 6b etc.) as well as of the host (euthymic NMRI-mice conditioned with dextran sulfate 500 or cyclosporin A, athymic nude mice etc.) on the course, morphology and outcome of the Listeria infection was investigated. From the experimental models used and the studies performed much could be learned concerning the factors that determine the histomorphological manifestations of listeriosis in humans.

Animals↗
PubMed1988

Alteration of non-specific resistance to infection with Listeria monocytogenes.

The experimental infection of murine hosts with Listeria monocytogenes is often used as a model for cell-mediated immunity. However, the natural immunity or non-specific resistance to listeriosis can be influenced by the parasite itself and also by a wide array of endogenous and exogenous host factors. The most important host factor in inbred mouse strains is their genetically determined susceptibility or resistance to Listeria monocytogenes. Secondly, the age of the mice is crucial for the outcome of infection. Resistance is only slowly developed by newborn mice, while aged mice possess an increased non-specific resistance as compared to young adult animals. Resistance is further influenced by the nutritional status, by pregnancy or by a simultaneous second antigenic stimulation. Regarding exogenous factors, macrophage blocking agents can totally abolish the resistance to listeriosis, while a lot of immunomodulating agents, such as BCG, killed Bordetella pertussis or Propionibacterium acnes organisms, lipopolysaccharides, suramin etc., can either increase or decrease the resistance. The mononuclear phagocyte system seems to be the main target of all these immunomodifiers. The timing between listeria infection and application of the immunomodulator determines the effect on non-specific resistance. A simultaneous injection of parasite and immunomodulator results in a decrease of resistance, while the application of immunoadjuvants several days before infection can dramatically increase the resistance to listeriosis. The delicate equilibrium of the mononuclear phagocyte system must therefore be taken into account, when infection with Listeria monocytogenes is used to test for immune-modifying agents, which are intended for use in humans or animals.

Adjuvants, Immunologic↗
PubMed1988

Pathogenicity of Listeria monocytogenes in comparison to other Listeria species.

In different mouse models the pathogenicity of various strains of Listeria monocytogenes and of other Listeria spp. was evaluated. Although quantitative differences of virulence among strains of L. monocytogenes are found, all isolates have to be regarded pathogenic unless essential virulence factors, such as protein composition of the cell wall or hemolysin production, are lacking. Besides L. monocytogenes, only Listeria ivanovii is able to multiply in the murine host, though definitely to a lesser extent. The other Listeria spp., such as Listeria innocua, Listeria welshimeri and Listeria seeligeri, have to be regarded as non-pathogenic.

Animals↗
PubMed1988

Therapy of experimental listeriosis--an evaluation of different antibiotics.

The therapeutic activities of various antibiotics were evaluated in two murine models, i.e. the infection of normal mice as well as of nude mice. Coumermycin and rifampicin were the most active drugs, since not only inhibition of multiplication but also rapid elimination of Listeria monocytogenes could be achieved in normal and immunocompromised animals. Ampicillin was the most active beta-lactam antibiotic followed by azlocillin. The other beta-lactam antibiotics were definitely less active. The combination of ampicillin with gentamicin expressed no synergistic effect in vivo. Co-trimoxazole as well as ciprofloxacin were of moderate therapeutic value. The bacteriostatic drugs such as tetracycline and erythromycin were able to inhibit the bacterial multiplication in the normal mouse but not in the immunocompromised host. Thus an optimal drug for therapy of listeriosis does not yet exist.

Aminocoumarins↗
PubMed1988

Inhibitory effect of tetracycline and doxycycline on resistance of mice to infection with a tetracycline-resistant strain of Listeria monocytogenes.

By transposon mutagenesis a tetracycline-susceptible strain of Listeria monocytogenes (MIC 1 mg/l. for tetracycline and 0.25 mg/l. for doxycycline) was rendered resistant (MIC 64 mg/l. for tetracycline and 16 mg/l. for doxycycline). Infection of mice with this resistant strain led to an acute infection. Treatment with 2 x 2 mg tetracycline per day did not influence the course of infection during the first 3 days, indicating that the nonspecific resistance, mediated mainly by macrophages and granulocytes, was not affected by this treatment. The second phase of infection, characterized by a continuous resistance to infection due to macrophages activated by T-lymphocytes was, however, definitely hampered. Even acquired immunity to a secondary infection was impaired by treatment with tetracycline, indicating that cell-mediated immunity can be blocked. The course of infection of athymic, nude mice which are unable to build up a cell-mediated immune response, was not affected by tetracycline treatment. Doxycycline expressed the same activities as tetracycline.

Animals↗
PubMed1988

[Effect of Propionibacterium granulosum KP-45 on the resistance to Listeria monocytogenes and Salmonella typhimurium infections].

Killed bacterial cells of Propionibacterium granulosum KP-45 were found to be potent modifiers of non-specific resistance of mice against infection with either Listeria monocytogenes or Salmonella typhimurium. Injection of P. granulosum 7 days prior to infection resulted in marked splenomegaly. Disseminated acute inflammatory foci were found histologically in the liver. These mice were apparently less susceptible to infection, since definitely lower bacterial counts were determined. Simultaneous application of both P. granulosum KP-45 and L. monocytogenes resulted, however, in increased susceptibility of mice to infection, since definitely higher bacterial counts were found and the inflammatory reaction to infection was markedly enhanced.

Adjuvants, Immunologic↗
PubMed1988

Therapeutic activity of teicoplanin on experimental listeriosis compared with that of vancomycin and ampicillin.

Several strains of Listeria monocytogenes and other Listeria spp. are without exception susceptible to teicoplanin (MIC 0.25 mg/l). Vancomycin as well as ampicillin are likewise active. A bactericidal effect of teicoplanin was only achieved at rather high concentrations and after incubation of several hours. There is no synergistic effect between teicoplanin and gentamicin. The therapeutic activity of teicoplanin as well as vancomycin in mice infected with L. monocytogenes is low. The efficacy of ampicillin could not be achieved. Treatment of chronically infected athymic, nude mice with teicoplanin is ineffective. Consequently, teicoplanin is not able to replace ampicillin in the therapy of listeriosis.

Ampicillin↗
PubMed1988

Comparative activities of norfloxacin and fleroxacin in experimental infections due to Salmonella typhimurium and Escherichia coli.

Norfloxacin and fleroxacin displayed similar in-vitro activity against test strains of Escherichia coli (MIC 0.06 mg/l) and Salmonella typhimurium (0.125 mg/l). Septicaemic infection of mice with E. coli could be almost cured by quinolones but not by ampicillin. Fleroxacin was more potent than norfloxacin. Infection of mice with S. typhimurium was much more difficult to treat. In spite of higher doses the bacterial counts remained at a considerable level. Again, fleroxacin was more active in vivo than norfloxacin.

Animals↗
PubMed1988

Levels of Listeria monocytogenes hemolysin are not directly proportional to virulence in experimental infections of mice.

The sulfhydryl-activated hemolysin of Listeria monocytogenes has been implicated in the virulence of the bacteria. Although loss of hemolytic activity by means of transposon mutagenesis is accompanied by loss of virulence in the mouse infection model, a direct relationship between in vitro production of hemolysin and virulence was not observed. Noticeable deviations in the extent of hemolysin production appeared to leave virulence unaffected.

Animals↗