Infect Immun, April 1998, p. 1570-1578, Vol. 66, No. 4
0019-9567/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
University Department of Paediatric
Gastroenterology,
Received 8 October 1997/Returned for modification 13 November
1997/Accepted 22 January 1998
Attaching and effacing (A/E) lesion formation is central to
enteropathogenic Escherichia coli (EPEC) pathogenesis.
In vitro experiments with human epithelial cell lines have implicated
virulence plasmid-encoded bundle-forming pili (BFP) in initial
binding and intimin in intimate attachment and A/E lesion formation.
This study investigated the role of BFP and intimin in EPEC
interactions with pediatric small intestinal biopsy tissue in in vitro
organ culture. Organ culture infections (2 to 8 h) were performed
with E2348/69 (a wild-type EPEC O127:H6 clinical isolate) and
E2348/69 derivatives including CVD206 (eae deficient),
CVD206(pCVD438) (eae-complemented CVD206),
CVD206(pCVD438/01) (expressing intimin, which is nonfunctional due
to a single amino acid substitution), JPN15 (spontaneous EPEC
adherence factor virulence plasmid-cured E2348/69), and 31-6-1(1)
(E2348/69 with a TnphoA insertion inactivation mutation in
the virulence plasmid-encoded bfpA gene). Scanning and
transmission electron microscopy revealed that after 8 h E2348/69 and CVD206(pCVD438) (both Int+ BFP+)
adhered to all specimens, causing A/E lesions with surrounding microvillous elongation. JPN15 and 31-6-1(1) (both Int+
BFP
) adhered and caused A/E lesions although bacteria
adhered in "flat," two-dimensional groups. CVD206 and
CVD206(pCVD438/01) (both Int
BFP+) did
not adhere to any sample, and no pathological tissue changes were seen.
Thus, in human intestinal organ culture, BFP do not appear to be
involved in the initial stages of EPEC nonintimate adhesion but are
implicated in the formation of complex, three-dimensional colonies via
bacterium-bacterium interactions. Intimin appears to play an essential
role in establishing colonization of EPEC on pediatric small intestinal
tissue.
*
Corresponding author. Mailing address: University
Department of Paediatric Gastroenterology, Royal Free Hospital, Pond
St., London, NW3 2QG, United Kingdom. Phone: 171 8302783. Fax: 171 8302146. E-mail: adphill{at}rfhsm.ac.uk.
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