To further our
understanding of the
virulence potential of
Bacillus megaterium strains,
cell association and invasion assays were conducted
in vitro by infecting
human enterocytes (
Caco-2 cells) with 53
strains of this bacterium isolated from
honey. Two series of experiments were performed (i)
necrosis and
cell detachment assays with the supernatants of bacterial
culture filtrates from 16-h
cultures and (ii) adhesion/invasion assays in which cultured
enterocytes incubated with
bacteria from 3-h
cultures were resuspended in Dulbeccos modified
Eagles medium and
chloramphenicol. The detachment of
Caco-2 cells was evaluated by
staining the
cells with
crystal violet.
Necrosis was assessed by
fluorescence microscopy of
cells labeled with
propidium iodide.
Association (adhesion plus invasion) was determined by plate counts and invasion in an
aminoglycoside protection assay. The results showed that spent
culture supernatants detached and necrotized
Caco-2 cells in a
strain-dependent manner. Seven out of 53 B. megaterium filtered
culture supernatants caused complete
cell detachment.
Suspensions of these same bacterial
strains adhered and invaded
enterocytes in 2-h
infection experiments. To our
knowledge, this is the first
report on the interaction between B. megaterium and intestinal epithelial
Caco-2 cells (AU)