Structural and functional effects of Bordetella avium infection in the turkey respiratory tract

Abstract

<p>Following aerosol exposure to virulent Escherichia coli, lung and tracheal samples were collected from Bordetella avium-infected (BA+) and B. avium-free (BA-) turkeys for bacterial quantitation and histopathologic examination. Pulmonary clearance of E. coli was not significantly different between BA+ and BA- groups, however numbers of E. coli isolated from trachea were significantly greater in BA+ turkeys compared with BA- turkeys. Air sacculitis was more common and more severe in BA+ turkeys;Tracheal adherence and colonization by E. coli were determined using an in vivo bacterial adherence assay. Compared with BA- turkeys, BA+ turkeys had significantly greater numbers of E. coli in their tracheas. Mechanisms for adherence and colonization by E. coli were not found;Pulmonary lesions and localization of bacteria in the respiratory tract were determined in turkeys experimentally infected with B. avium. Bordetella avium was isolated from trachea and primary bronchi of all BA+ turkeys, but was never isolated from lung parenchyma. Acute purulent bronchitis associated with B. avium colonization of the primary bronchi subsided by 3 weeks postinoculation. Bronchus-associated lymphoid tissue was histologically similar in BA+ and BA- turkeys and consisted of discrete lymphoid nodules, which were more numerous and widely distributed along primary bronchi of BA+ turkeys;Metabolic activity of tracheal epithelium was evaluated using a tetrazolium chloride reduction assay. Morphology of epithelium was determined by light microscopy in turkey tracheal organ cultures (TOCs) exposed to live B. avium, formalin killed B. avium, B. avium sonicate, heat-inactivated sonicate, culture supernatant, heat-inactivated culture supernatant, phosphate buffered saline, or brain heart infusion broth. Although the bacterial sonicate containing heat-labile toxin was lethal for turkeys, neither the sonicate nor any other B. avium fraction significantly affected the metabolism or morphology of turkey TOCs.</p>