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Infection and Immunity, October 1999, p. 5447-5454, Vol. 67, No. 10
Discipline of Pathology, University of
Tasmania, Hobart, Tasmania 7001, Australia
Received 30 April 1999/Returned for modification 24 May
1999/Accepted 15 July 1999
Our past work has shown that long, flexible type IV pili (single or
in bundles) are the predominant pili expressed on fecal isolates of
diarrhea-associated species of Aeromonas (Aeromonas veronii biovar sobria and A. caviae). They represent
a family of type IV pili which we have designated Bfp (for
bundle-forming pili). Reports from Japan suggest that Bfp are
intestinal colonization factors. This study presents compelling
evidence to support this conclusion. Aeromonas bacteria
and/or Bfp purified from a strain of A. veronii biovar
sobria were shown to adhere to epithelial and intestinal cell lines,
freshly isolated human enterocytes, and fresh and fixed human and
rabbit intestinal tissues, as determined by light and electron
microscopy and immunohistochemical detection. Removal of Bfp by
mechanical means decreased adhesion to cell lines by up to 80%.
Purified Bfp blocked adhesion of the test strain to intestinal cells in
a dose-dependent manner. Adhesion was also blocked by the Fab fraction
of anti-Bfp immunoglobulin G. Moreover, ultrastructural studies
(ruthenium red staining and transmission and scanning electron
microscopy) demonstrated for the first time that Aeromonas
adhesion to human enterocytes is pilus mediated and suggested that Bfp
may also promote colonization by forming bacterium-to-bacterium
linkages. Bfp-positive isolates examined for type IV pilus-mediated
twitching motility in agar and slide culture assays developed for
Pseudomonas aeruginosa did not, however, exhibit this function.
0019-9567/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Functional Characterization of Type IV Pili
Expressed on Diarrhea-Associated Isolates of Aeromonas
species
*
Corresponding author. Mailing address: Discipline of
Pathology, University of Tasmania, GPO Box 252-29, Hobart 7001, Tasmania, Australia. Phone: 61 3 6226 4835. Fax: 61 3 6226 4833. E-mail: S.M.Kirov{at}utas.edu.au.
Present address: School of Agricultural Science, University of
Tasmania, Hobart, Tasmania 7001, Australia.
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