Background-Strains of Bacteroides fragilis producing a 20 kDa protein toxin
(B fragilis toxin (BFT) or fragilysin) are associated with diarrhoea in an
imals and humans. Although in vitro results indicate that EFT damages intes
tinal epithelial cells in culture, the effects of BFT on native human colon
are not known.
Aims-To examine the electrophysiological and morphological effects of purif
ied BFT-2 on human colonic mucosa in vitro.
Methods-For resistance (EP) measurements, colonic mucosa mounted in Ussing
chambers was exposed to luminal or serosal BFT-2 (1.25-10 nM) and after fou
r hours morphological damage was measured on haematoxylin and eosin stained
sections using morphometry. F actin distribution was assessed using confoc
al microscopy.
Results-Serosal BFT-2 for four hours was four-, two;, seven-, and threefold
more potent than luminal BFT-2 in decreasing resistance, increasing epithe
lial H-3-mannitol permeability, and damaging crypt and surface colonocytes,
respectively. (p<0.05). Confocal: microscopy showed reduced colonocyte F a
ctin staining intensity after exposure to BFT-2.
Conclusions-BFT-2 increases human colonic permeability and damages human co
lonic epithelial cells in vitro. These effects may be important in the deve
lopment of diarrhoea and intestinal inflammation caused by B fragilis in vi
vo.