Scanning electronmicroscopic studies of Bordetella bronchiseptica on the rabbit tracheal mucosa

This study used scanning electron microscopy to examine how Bordetella bronchiseptica, a natural rabbit respiratory pathogen, interacts with rabbit tracheal epithelial cells in organ culture. Two days after inoculation, B. bronchiseptica showed intimate associations with ciliated epithelial cells, with bacteria becoming entangled in tufts of cilia and extrusions of infected epithelial cells visible throughout the infected mucosa. In contrast, Staphylococcus aureus, which has no special respiratory affinity, caused ciliary damage and epithelial cell extrusion but showed minimal intimate contact with cilia and was largely lost during specimen preparation. The authors suggest that B. bronchiseptica's specific interaction with respiratory cilia may be important for its pathogenesis, allowing the bacterium to persist in the respiratory tract despite mucociliary clearance mechanisms. Results were consistent across multiple bacterial strains and in tissues from rabbits with naturally acquired B. bronchiseptica antibodies, supporting the biological relevance of these observations.

Key findings

• Bordetella bronchiseptica demonstrated intimate associations with rabbit tracheal cilia, with large numbers of bacteria becoming entangled in ciliary tufts two days post-infection
• Staphylococcus aureus caused similar epithelial damage but showed no intimate interactions with cilia, suggesting B. bronchiseptica has a specific tropism for respiratory epithelium
• The specific ciliary interaction of B. bronchiseptica may facilitate bacterial persistence in the respiratory tract and resistance to mucociliary clearance mechanisms
• Results were consistent across different B. bronchiseptica strains and in tissues from immunologically primed rabbits, indicating a reproducible pathogenic mechanism