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Biomedical subjects

H Hof

Publications and source records attributed to H Hof.

At least 127 records · Page 7Linked to original sources
PubMed1988

Pseudoappendicitis caused by Plesiomonas shigelloides.

A 20-year-old patient was hospitalized with clinical signs of acute appendicitis. After surgery, the histological findings in the appendix and a lymphatic node suggested the diagnosis of pseudoappendicitis caused by Plesiomonas shigelloides, which was isolated in pure culture from the lymphatic node. The strain of P. shigelloides was found to elaborate a heat-stable toxin and harbored two plasmids of 280 and 4 kilobases. A large plasmid has previously been implicated as a virulence marker in P. shigelloides infections.

Adult↗
PubMed1988

[Antimicrobial therapy with nitroheterocyclic compounds, for example, metronidazole and nitrofurantoin].

Nitroheterocyclic compounds, such as metronidazole and nitrofurantoin, are widely used in medical practice for the treatment of infectious diseases. Indeed, they exhibit a strong antimicrobial effect, which is directed not only against several groups of bacteria but also against certain protozoa and even worms. The nitrogroup coupled onto a heterocyclic structure, for example an imidazole, a thiazole or a furan ring, represents the proper site of effect. A priori the nitrogroup is, however, inactive. It has to be activated by microbial nitroreductases after penetration into the microbial cell. Those microorganisms which possess an anaerobic metabolism exhibit marked nitroreductase activity. The intracellularly produced intermediate products attack the chromosomal DNA of the target cell. Consequently, diverse mutations may occur. Partially, these chromosomal damages can be compensated by an SOS repair mechanism, which is under the control of the uvrB, lexA and polA genes. SOS repair-deficient mutants are much more susceptible to nitrocompounds than repair-proficient strains. Principally, the genotoxic activity of nitrocontaining compounds can also be expressed in eukaryotic cells of human or animal origin. This virtual property does not, however, prohibit clinical use, since until now no evidence of increased cancer incidence has been observed after rational therapy with nitrocompounds.

Animals↗
PubMed1987

[Cutaneous diphtheria from Africa].

A 31-year-old woman returned to her native Germany, after a two-year stay in Tanzania, suffering from cutaneous diphtheria which had spread to nose and throat. One of her three children, a four-year-old boy, also had Corynebacterium diphtheria in his throat, without any symptoms. Both mother and child had been immunized against diphtheria.

Adult↗
PubMed1987

The influence of killed Propionibacterium granulosum on experimental infection with Escherichia coli.

Mice infected subcutaneously with 5 X 10(3) viable cells of Escherichia coli ATCC 25922 incorporated in liquified agar developed a systemic infection. Increasing bacterial numbers could be recovered from the liver at several days following infection. Ultimately, the animals died 6 days after infection. Treatment of mice with 1 mg killed Propionibacterium granulosum KP-45 lead to an increased spleen weight at day 7 after intraperitoneal injection. Hence, the animals were highly susceptible to the lethal action of endotoxin. They were, however, markedly protected against infection with E. coli, since definitely lower bacterial counts were found in the liver of pretreated mice in comparison to controls.

Animals↗
PubMed1987

Activities of metronidazole and niridazole against Trichomonas vaginalis clinical isolates.

The activities of niridazole and metronidazole against Trichomonas vaginalis C1-NIH and six isolates of clinical origin were compared using the in-vitro assay technique. Under the standard anaerobic assay conditions both metronidazole and niridazole were highly effective at low concentrations against all the strains used. However niridazole, in contrast to metronidazole, was equally effective in the aerobic assay, a feature which may be exploited in the chemotherapy of patients with refractory trichomoniasis.

Animals↗
PubMed1987

Marker exchange mutagenesis of the aerolysin determinant in Aeromonas hydrophila demonstrates the role of aerolysin in A. hydrophila-associated systemic infections.

We report here on the isolation of isogenic strains of Aeromonas hydrophila AB3 deleted for a segment of the aerolysin gene. All aer mutants obtained lacked the 49-kilodalton aerolysin gene product and were neither hemolytic for blood erythrocytes nor cytotoxic for Chinese hamster ovary tissue culture cells. One such mutant, AB3-5, was used in a mouse toxicity model to evaluate the role of aerolysin in the pathogenesis of A. hydrophila infections. The strain had a 50% lethal dose (LD50) of greater than 10(9) as compared with the parental strain which had an LD50 of 5 X 10(7). Reintegration of the deleted segment into AB3-5 resulted in an LD50 of 6 X 10(7) cells for this revertant. Furthermore, all mice injected with a sublethal dose of the parental strains developed necrotic lesions; this was never obtained with the aerolysin-deficient strain AB3-5. More importantly, specific neutralizing antibody to aerolysin was detected in mice surviving A. hydrophila infection, demonstrating that aerolysin is produced during the course of systemic A. hydrophila infections.

Aeromonas↗
PubMed1987

Tn916-induced mutations in the hemolysin determinant affecting virulence of Listeria monocytogenes.

A genetic determinant essential for hemolysin production by Listeria monocytogenes has been inactivated by insertion of transposon Tn916 into L. monocytogenes DNA. The transposon was transferred by means of conjugation of a streptomycin-resistant L. monocytogenes recipient strain with Streptococcus faecalis CG110 on membrane filters. Among the tetracycline-resistant transconjugants, mutants were detected which had lost hemolytic activity. When tested in a mouse model, these mutants appeared to have lost the virulence that characterizes the parental strain. An extracellular protein of 58,000 apparent molecular weight was eliminated in the nonhemolytic mutants. In some of the mutants, the decrease in the production of the 58,000-dalton protein was accompanied by the production of a new protein of 49,000 apparent molecular weight. Hemolytic revertants regained the hemolytic phenotype and virulence and produced the extracellular protein that characterizes the recipient strain. Hybridization studies with Tn916 DNA indicated that the transposon is present in EcoRI and HindIII fragments of the nonhemolytic mutants. Single copies of Tn916 were detected in the chromosomal DNA of two of the three nonhemolytic mutants that were studied in detail. In hemolytic, tetracycline-sensitive revertants Tn916 appeared to be completely excised from the chromosome.

DNA Transposable Elements↗
PubMed1987

[New species of the genus Listeria: Listeria seeligeri].

Listeria seeligeri is a recently described species which shares 28% to 1% DNA relatedness with the other species of the genus Listeria. G + C% content of the type strain is 36. Peptidoglycan type (variation A1 gamma) as well as teichoic acids are identical to those found in L. monocytogenes. L. seeligeri can be easily distinguished from the other species using the following markers: hemolysis (CAMP-tests with Staphylococcus aureus and Rhodococcus equi) and acid production from D-xylose, L-rhamnose and alpha-methyl-D-mannoside. No specific antigen allow to characterize L. seeligeri strains which belong to serogroups 1/2 (81%), 4 (12%) and 6 (6%). 85% of these strains proved to be phage typable. So far, more than 100 strains were isolated, mainly in Europe, from environment and animal healthy carriers. Unless one case of meningitis in human, strains of this species are experimentally non virulent.

Animals↗
PubMed1987

Mode of action of nitro-heterocyclic compounds on Escherichia coli.

The inhibitory and bactericidal activities of several different nitro-heterocyclic compounds, such as nitrofuran, nitronaphthofuran, nitrobenzofuran, nitroimidazole and nitrothiazole, were assessed in vitro. All these substances except nitroimidazole were active against Escherichia coli, though to different degrees. Under anaerobic test conditions the antibacterial activity increased slightly. Nitroreductase-deficient mutants, however, were highly resistant to all nitro-compounds, indicating that only when the nitro-group is reduced to these agents get into an active antibacterial form. SOS repair-deficient strains were much more susceptible to the nitro-containing substances than repair-proficient counterparts, indicating that damage to bacterial DNA is the essential mechanism of antibacterial activity of all nitro-heterocyclic compounds.

Escherichia coli↗
PubMed1987

Therapeutic activities of nitrothiazoles against trichomonads.

Certain nitrothiazole derivatives, such as niridazole (Ba 32644, Ambilhar), exert pronounced activities against several trichomonad strains when tested under anaerobic conditions comparable to those of the nitroimidazole derivatives. Few compounds of the nitrothiazole group, however, are markedly less active in vitro. The in vivo activity of the nitrothiazole derivatives as determined in mice infected subcutaneously with T. foetus, is as good as that of metronidazole. A nitrothiazole derivative with a laminar side chain is inactive in vivo after oral administration, although it shows pronounced antitrichomonad activity in vitro.

Animals↗
PubMed1986

[Acute purulent Listeria seelingeri meningitis in an immunocompetent adult].

Within the genus Listeria, the species L. monocytogenes most frequently causes disease in animals and humans. L. Seeligeri, a species recently described, has been considered experimentally nonpathogenic so far. The authors report the first case of human infection in a previously healthy adult presenting with acute purulent meningitis due to L. seeligeri. The patient recovered promptly after a course of ampicillin and gentamicin, but developed severe neurological sequelae (epilepsy, hydrocephalus) one year after the acute episode. The pathogenic properties of this isolate were investigated in two experimental animal models and the results were as follows. The clinical isolate of L. seeligeri was able to colonize the spleens of adult mice without bacterial multiplication, in contrast to the type strain of L. seeligeri (no colonization) and to a L. monocytogenes strain (colonization and multiplication). Previous infection of adult mice with the clinical L. seeligeri isolate protected moderately against spleen colonization and bacterial multiplication after challenge with L. monocytogenes. No lethal effect was observed after inoculation of suckling mice with the clinical L. seeligeri isolate, in contrast to L. monocytogenes strains. Thus, L. seeligeri, previously described as experimentally nonpathogenic for mice, may in fact be a heterogeneous species regarding its pathogenicity, and include strains that may cause life-threatening diseases in humans.

Humans↗
PubMed1986

Influence of cloned Escherichia coli hemolysin genes, S-fimbriae and serum resistance on pathogenicity in different animal models.

The virulence of the uropathogenic E. coli strain 536 (O6:K15:H31) which produces the S-fimbrial adhesin (Sfa+), is serum-resistant (Sre+) and hemolytic (Hly+) and its derivatives were assessed in five different animal models. Cloned hemolysin (hly) determinants from the chromosomes of O6, O18 and O75 E. coli strains and from the plasmid pHly152 were introduced into the spontaneous Sfa-, Sre-, Hly- mutant 536-21 and its Sfa+, Sre+, Hly- variant 536-31. As already demonstrated for the 536-21 strains (Infect. Immun. 42: 57-63) the O18-hly determinant but not the plasmid-encoded hly determinant of pHly152 transformed into 536-31 contribute to lethality in a mouse peritonitis model. Similar results were obtained with both Hly- host strains and their Hly+ transformants in a chicken embryo test and in a mouse nephropathogenicity assay in which the renal bacterial counts were measured 15 min to 8 hours after i.v. infection. S-fimbriae and serum resistance had only a marginal influence in these three in vivo systems. In contrast all three factors, S-fimbriae, serum resistance and hemolysin, were necessary for full virulence in a respiratory mouse infection assay. In a subcutaneously-induced sepsis model in the mouse restoration of S-fimbriae and serum resistance and separately chromosomally-encoded hemolysis increased virulence to a level comparable to that of the parental 536 strain.

Animals↗
PubMed1986

The effect of coumermycin on experimental listeriosis.

The in vitro susceptibilities of Listeria spp. to coumermycin and novobiocin were tested. Coumermycin (0.015-0.12 mg/l) displayed lower minimum inhibitory concentrations than novobiocin (1-2 mg/l). There was only a narrow range of susceptibilities among 52 strains of Listeria spp. Bactericidal activity, however, could not be found. The in vivo activities of coumermycin were tested in mice. In normal adult mice infected with a virulent strain of L. monocytogenes the bacterial counts decreased rapidly after parenteral treatment with 2 mg twice daily but not after oral administration of 4 mg twice daily. Bacterial eradication was so effective that an immune response was prevented. Even in congenitally athymic mice a complete cure could be achieved.

Administration, Oral↗
PubMed1986

[Virulence of Listeria welshimeri].

The species L. welshimeri consists of non-pathogenic bacteria. 16 different strains which were characterized biochemically were unable to multiply within adult NMRI mice after injection of a high dose of about 10(7) bacteria. Even macrophage depleted animals, which were obtained by treatment with highmolecular dextran sulfate, could eliminate L. welshimeri. 5 day old baby mice were resistant against L. welshimeri. L. innocua was as avirulent as L. welshimeri, whereas L. monocytogenes was virulent, since these bacteria multiplied in adult animals, killed macrophage depleted adult mice as well as baby mice after injection of low doses.

Animals↗