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Pili of Bordetella avium: expression, characterization, and role in in vitro adherence
Abstract:
Electron microscopy revealed pili on all isolates of Bordetella avium and B. avium-like bacteria examined. Trypticase soy broth (TSB) and 2% peptone agar were the best media for promoting pilus expression. Cultures grown at 37 or 42 C had similar pilus production, whereas cultures grown at 18 C produced few or no pili. Pilus expression of the Art Vax strain was best when that strain was grown in TSB, but the strain yielded fewer pili than B. avium and B. avium-like isolates grown under the same cultural conditions. B. avium pili had a diameter of 2.0 nm, ranged in length from 370 nm to 1500 nm, and had a protein subunit molecular mass of about 13,100 daltons. Purified pili from B. avium did not hemagglutinate guinea pig erythrocytes, and a 1:20 dilution of hyperimmune antisera against B. avium pili did not block the hemagglutinating activity of whole-cell preparations of B. avium. In the indirect immunofluorescence test, B. avium isolates and the Art Vax strain adhered to the tracheal explants of turkeys, but B. avium-like isolates did not. Purified pili from B. avium adhered to the surface of the mucosal lining of the tracheal explants, and hyperimmune antisera against B. avium pili blocked the in vitro adherence of whole-cell preparations of B. avium. It was concluded that pili of B. avium are involved in the in vitro attachment of that bacterium to the mucosal surface of turkey tracheal explants.
Insights
Bordetella avium pili are crucial for bacterial attachment to turkey tracheal tissues. Optimal growth conditions enhance pilus production, aiding in understanding bacterial adhesion mechanisms.
Area of Science:
- Microbiology
- Bacterial Pathogenesis
- Veterinary Science
Background:
- Bordetella avium and related bacteria are significant in avian respiratory diseases.
- Pili, hair-like appendages on bacterial surfaces, are often implicated in adhesion and colonization.
- Understanding the role of pili in B. avium attachment is essential for disease control.
Purpose of the Study:
- To investigate the presence and characteristics of pili in Bordetella avium isolates.
- To determine the optimal conditions for pilus expression in B. avium.
- To elucidate the role of B. avium pili in the attachment to turkey tracheal explants.
Main Methods:
- Electron microscopy was used to visualize pili on bacterial isolates.
- Various culture media and temperatures were tested to optimize pilus production.
- Indirect immunofluorescence assays and in vitro adherence tests with turkey tracheal explants were performed.
Main Results:
- Pili were observed on all Bordetella avium and B. avium-like isolates.
- Trypticase soy broth and 2% peptone agar at 37°C or 42°C promoted maximal pilus expression.
- Purified B. avium pili adhered to turkey tracheal mucosal surfaces, and antisera blocked this attachment, indicating pili's role in adherence.
Conclusions:
- Pili are a consistent feature of Bordetella avium and are involved in its in vitro attachment to turkey tracheal mucosal surfaces.
- Specific growth conditions significantly influence pilus expression, impacting bacterial adherence.
- These findings highlight the importance of pili as adhesins in the pathogenesis of B. avium infections in turkeys.