In vitro interaction between Bacillus megaterium strains and Caco-2 cells

Resum

To further our understanding of the virulence potential of Bacillus megaterium strains, cell association andinvasion assays were conducted in vitro by infecting human enterocytes (Caco-2 cells) with 53 strains of this bacteriumisolated from honey. Two series of experiments were performed: (i) necrosis and cell detachment assays with the supernatantsof bacterial culture filtrates from 16-h cultures and (ii) adhesion/invasion assays in which cultured enterocytesincubated with bacteria from 3-h cultures were resuspended in Dulbecco's modified Eagle's medium and chloramphenicol.The detachment of Caco-2 cells was evaluated by staining the cells with crystal violet. Necrosis was assessedby fluorescence microscopy of cells labeled with propidium iodide. Association (adhesion plus invasion) was determinedby plate counts and invasion in an aminoglycoside protection assay. The results showed that spent culture supernatantsdetached and necrotized Caco-2 cells in a strain-dependent manner. Seven out of 53 B. megaterium filtered culture supernatantscaused complete cell detachment. Suspensions of these same bacterial strains adhered and invaded enterocytes in2-h infection experiments. To our knowledge, this is the first report on the interaction between B. megaterium and intestinalepithelial Caco-2 cells. [Int Microbiol 2013; 16(1):27-33]