Aus dem Institut für Pathologie der Tierärztlichen Hochschule

88 Summary
Histopathology revealed partly severe lesions with necrosis, suppurative
bronchopneumonia, obliterative bronchiolitis and interstitial pneumonia in calves of
group 3 and 4 euthanised 21 days post infection with M. bovis. The lesions were
consistent with those described in literature. Beside M. bovis, other bacterial agents
were detected in lung tissues indicating promotion of secondary bacterial infections
due to M. bovis as described in literature.
Partly, abundant M. bovis-DNA could be found within necrotic areas and in the
exudate of suppurative bronchopneumonia by the in situ-hybridization method
established for this investigation. M. bovis-DNA was not detectable in the alveoli,
interstitial tissue, peribronchiolar lymphatic tissue and epithelium of the air ways as
described by BUCHENAU (2003) with specific antibodies directed against variable
surface proteins.
The investigation of the lung samples with a commercial monoclonal antibody
(MAB970), directed against not defined epitops of M. bovis, revealed M. bovisantigen
in similar areas as M. bovis-DNA detected by ISH. However, positive
reactions were found within the epithelium of bronchi and bronchioli also seen in M.
bovis negative control animals. These are possibly cross reactions of the antibody
with host structures.
It can be postulated, that M. bovis persists in the respiratory tract of experimentally
infected calves and is possibly excreted with the exudate in cases of suppurative
bronchopneumonia.
The factors, which enable M. bovis to persist in the lungs of infected cattle, are poorly
understood. With the in situ-hybridization another tool was established to investigate,
beside vspA, other gene sequences. Further investigations should also include the
possible participation of variable surface proteins in the ability of M. bovis to produce
biofilms.