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Expression of P and type 1 (F1) fimbriae in pathogenic Escherichia coli from poultry
C M Dozois1, S A Pourbakhsh, J M Fairbrother
1Département de pathologie et microbiologie, Faculté de médecine vétérinaire, Université de Montréal, St-Hyacinthe, Qué., Canada.
Abstract:
To investigate the expression of P and type 1 (F1) fimbriae in pathogenic avian Escherichia coli, fourteen pap+/fim+ E. coli isolates pathogenic for poultry were grown on four complex or minimal media, and examined for the presence of mannose resistant (MR) and mannose sensitive (MS) hemagglutination (HA), and for P or for type 1 (F1) fimbriae using immunofluorescence, immunodot, and immunoblot. In addition, isolates grown under different culture conditions were examined for adherence to frozen sections of chicken trachea. Twelve of the 14 isolates were divided into three groups based on adhesin expression in the different media. Isolates of all three groups exhibited strong MSHA reactions when cultures were grown serially in static broth, and expressed a subunit protein with an apparent molecular mass of 17 to 18.5 kDa, serologically related to the FIA major fimbrial subunit. There was a good correlation between MSHA and adherence to chicken tracheal sections. Isolates of group I only demonstrated MSHA and expression of F1A fimbriae after growth in static broth. Isolates of group II demonstrated MSHA and expression of F1A fimbriae after growth in all tested media whereas isolates of group III demonstrated expression of F1A fimbriae only after growth in static broth and minimal agar. Only the five group I isolates expressed MRHA associated with P fimbrial adhesins and expressed fimbriae with a major subunit protein of 18 kDa serologically related to the F11 major fimbrial subunit. None of these five isolates grown on complex solid media, where P but not type 1 fimbriae were expressed, adhered to tracheal sections. Results suggest that i) P fimbriae are not readily expressed in vitro by most pap+/fim+ avian E. coli isolates; ii) environmental control of phase variation of type 1 fimbriae differs among pathogenic avian E. coli; and iii) receptors for type 1, but not for P fimbriae, are present in chicken tracheal mucosa.
Insights
Pathogenic avian E. coli express type 1 fimbriae, aiding adherence to chicken tracheas. P fimbriae expression is limited in vitro, suggesting type 1 fimbriae are key for avian E. coli infections.
Area of Science:
- Microbiology
- Veterinary Science
- Bacterial Pathogenesis
Background:
- Pathogenic avian Escherichia coli (E. coli) utilize fimbriae for host colonization.
- Understanding the expression and role of P and type 1 fimbriae is crucial for avian health.
Purpose of the Study:
- To investigate the expression of P and type 1 fimbriae in pathogenic avian E. coli.
- To determine the correlation between fimbrial expression and adherence to chicken tracheal tissues.
Main Methods:
- Culturing 14 pathogenic avian E. coli isolates on various media.
- Assessing mannose-resistant (MR) and mannose-sensitive (MS) hemagglutination (HA).
- Utilizing immunofluorescence, immunodot, and immunoblot assays for fimbrial detection.
- Examining bacterial adherence to frozen chicken tracheal sections.
Main Results:
- Most isolates expressed type 1 fimbriae (F1A) and showed mannose-sensitive hemagglutination (MSHA), correlating with tracheal adherence.
- P fimbriae expression was limited and not associated with adherence in most isolates.
- Environmental conditions significantly influenced type 1 fimbriae expression and phase variation.
Conclusions:
- Type 1 fimbriae are important for avian E. coli adherence to chicken tracheas.
- P fimbriae are not readily expressed in vitro by most pathogenic avian E. coli.
- Receptors for type 1 fimbriae, but not P fimbriae, are present on chicken tracheal mucosa.