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Institute of Molecular Pathogenesis (IMP)

Research area of Pathology and Electron Microscopy

Research in the Research Area of Pathology and Electron Microscopy focuses on host-pathogen interactions at the mucosal barriers of the respiratory and digestive tract in infectious diseases of farm animals. Reactions and damages of the mucosal immune system as first site of contact are of particular interest. Electron microscopy is used to investigate interactions between bacteria (especially facultative and obligate intracellular bacteria) and their target tissues/cells in vivo and in cell culture, and to correlate ultrastructure of bacteria with their cultural and molecular characteristics.

Main current research topics

Paratuberculosis

Paratuberculosis is an economically highly important disease of cattle and small ruminants caused by Mycobacterium avium ssp. paratuberculosis. Host-pathogen interactions during the long clinically inapparent incubation period prior to the onset of disease are not well known, but are a major determinant to the outcome of disease. An experimental model of infection has been established in goats (collaboration with Dr. H. Köhler, Workgroup Mycobacteria). Using this model, lesions, distribution of MAP and cellular reactions at the sites of lesions are investigated during the clinically inapparent incubation period.

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Swine dysentery

Swine dysentery (SD), a multifactorial disease caused by Brachyspira hyodysenteriae, has a major impact on swine production. An infection model for SD was established and characterized in collaboration with Dr. W. Herbst and Dr. S. Barth (JLU Gießen). It was used to compare host pathogen interactions for isolates of Brachyspira hyodysenteriae with different virulence and to collect tissues during the acute disease, healing and recovery. The tissues collected are used to study ways of invasion ultrastructurally. Cellular reactions in the intestinal mucosa are detected by multicolor immune fluorescence during acute disease, healing and recovery.

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Chlamydial infections

Development and healing of lesions are investigated in experimental models of intrapulmonary infection of calves with Chlamydia psittaci of non-avian origin and Parachlamydia spp. as established by Prof. Dr. Dr. P. Reinhold. Host-pathogen reactions are compared in the severe acute infections, infections treated with various antibiotics and persistent clinically inapparent infections.

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Norovirus infection of calves

Field infections of calves with bovine norovirus may induce clinical signs in calves similar to those seen in human norovirus infection. An experimental infection was established and characterized in calves that may serve as a homologous large animal model for the human norovirus infection (collaboration with Dr. P. Otto, Workgroup Rotaviruses/Noroviruses, Institute of Bacterial Infections and Zoonoses).

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Ultrastructural investigations

are used 

  • to support the characterization of new bacterial species (chlamydia/Dr. K. Sachse, mycoplasma/ Dr. M. Heller, Workgroup Chlamydiae and Mycoplasmas)
  • to study the interaction bacteria with host cells in cell culture (Chlamydia spp. with antigen presenting cells (Dr. M. Knittler, Institut of Immunology) and fibroblasts (PD Dr. J. Rödel, Friedrich-Schiller-University, Jena), MAP with epithelial cells (Dr. H. Köhler, Workgroup Mycobacteria) and Coxiella burnetti with macrophages (Prof. Dr. C. Menge; Workgroup Infection and Immunity))
  • to investigate the morphology of Coxiella burnetii maintained under cell-free culture conditions (Dr. A. Lührmann, Friedrich-Alexander-University Erlangen-Nürnberg)
  • to examine the interaction of bacteria and host tissues in tissue samples collected at autopsy from cases of experimental infections (Chlamydia spp., Brachspira hyodysenteriae, MAP and bovine norovirus)

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Methods

Methods used in the Research Area of Pathology/Electron Microscopy are

  • autopsies,
  • evaluation and photographic documentation of gross lesions,
  • collection of tissue samples during autopsies, of bacterial cultures and of infected cell cultures
  • preparation of samples for histologic, immunohistochemical and (immune) electron microscopic investigations (ultrathin sections, negative contrast, transmission and scanning electron microscopy)
  • evaluation of samples by light, fluorescence and electron (transmission and scanning) microscopy, photographic documentation, morphometry, statistics

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