Attachment of Mycoplasma pneumoniae to tracheal monolayer outgrowths

Mycoplasma pneumoniae is a human pathogen of the respiratory tract. It attaches to the ciliated respiratory epithelium by means of its attachment tip and the sialoglycoprotein receptor site on host cells. To study the mechanical and biochemical features of the attachment process, we developed a new in vitro biological model of respiratory tissue. The ciliated monolayer system involved a collagenase treatment of rodent tracheal explants, followed by incubation in Waymouth's MAB 87/3 medium. Epithelial migration led to the development of patches of cell monolayers both interior and exterior to the tracheal lumen. After seven days of incubation, monolayer patches contained 20 percent ciliated cells. Ciliary motion was active for several days after the explant was removed. When exposed to M. pneumoniae for two hours, the ciliated cells became covered with pathogen. The mycoplasmas were in close association with the host cell membranes, and could lie horizontally along the membrane when not physically held in a vertical orientation by cilia. Cytonecrosis developed within 48 to 72 hours.