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In vitro colonization of porcine trachea by Mycoplasma hyopneumoniae.

Porcine tracheae maintained in culture were used in order to study the colonization by Mycoplasma hyopneumoniae. Rings excised from tracheae of newborn piglets were infected with M hyopneumoniae strain BQ 14 and, after different incubation times, were examined by light and electron microscopy. Non-infected tracheal mucosae maintained a normal appearance for several days. Infected tracheal rings showed progressive colonization with concomitant progressive damage to the mucosal surface. Early on during the infection, few mycoplasmas occurred over a ciliated epithelium. As the infection progressed, there was gradual loss of cilia; mycoplasmas tended to form microcolonies and to accumulate over the remaining ciliated cells. Mycoplasmas, first seen at the apex of the cilia, were then seen deeper in the inter-ciliary space; some were even seen in contact with microvilli. In histological investigation, the final stage of the infection was characterized by a marked destruction of the epithelium with exfoliation of the epithelial cells. Infected mucosae showed typical damage caused by M hyopneumoniae, namely reduction of ciliary activity after 5 days, loss of cilia, and sloughing of ciliated cells. Our data indicate that porcine tracheal organ culture can be advantageously used to study colonization by M hyopneumoniae.