Dissertation to obtain a Master Degree in
Molecular Genetics and BiomedicineAims: To contribute to the evaluation of the pathogenic potential of Aeromonas, through the test of 24 Aeromonas spp. strains of Portuguese origin, for the adherence, invasion and cytotoxicity abilities in
mammal cells.
Rationale: Studies on other enteropathogens indicate that a pathogen must be able to attach to host target cells to cause gastrointestinal disease [Finlay and Falkow, 1997; Scoglio et al., 2001], via either
toxin production or host cell invasion, or both [Knutton, et al. 1987].
Results: 19 (79%) and 12 (50%) strains were found to have the ability to adhere and invade differentiated cells respectively while 22 (92%) and 13 (54%) strains had ability to adhere and invade undifferentiated Caco-2 cells. These results indicate that most Aeromonas spp. strains interact optimally with cultured human intestinal cells at cellular sites expressed in the brush border early in the
differentiation process of Caco-2 cells. In 13 (54%) strains it was observed an aggregative adhesion pattern as observed in other enteropathogens, including all clinical strains. 6 (25%) isolates express
both adherence and extracellular cytotoxicity, but preheating caused a decrease in the citotoxicity of the supernatants of 5 of these strains suggesting that the remainder clinical strain (A255) has the ability to produce extracellular heat-stable toxins. 17 (71%) isolates express cell contact dependent
cytotoxicity, but only 13 of these strains were able to invade Caco-2 cells, indicating the presence of others mechanisms of cell lysis not yet determined.
Conclusions: Aeromonas spp. strains isolated from water, food and food processing surfaces
showed adhesive, invasive and cytotoxic patterns similar or larger than clinical strains, suggesting that environmental Aeromonas spp. stains have the potential to cause human illness and that food and water sources may act as dissemination vehicles of this human pathogen with implication in the public health in Portugal
