Experimental infections of gnotobiotic piglets with Pasteurella septica (sero-group A) alone or with Mycoplasma hyopneumoniae

Abstract

In the apparent absence of other micro-organisms large numbers of a viable mucoid, sero-group A strain of Pasteurella septica produced acute or subacute disease when broth cultures were administered to young, gnotobiotic Large White piglets by intranasal or intratracheal inoculation. The piglets varied in their susceptibility to the organism. When disease was produced, the condition took several forms, including septicaemia, fibrinous pneumonia and fibrinous lesions of the thoracic serosae, fibrino-purulent joint and tendon lesions, or, occasionally, rhinitis, bronchopneumonic or interstitial pneumonic lesions. Some animals exposed to infection were unaffected although in them the organism became established in the nasopharynx and large gut where its presence elicited minor inflammatory changes. None of these abnormalities was produced by either bacteria-free filtrates of cultures or by broth. In Large White or Landrace gnotobiotic piglets, respectively exposed to infection by intratracheal or intranasal inoculation of a combination of a strain of Mycoplasma hyopneumoniae with the pasteurellae, the combined infection produced more severe pulmonary lesions than either infection singly in 4 of 6 animals.