The mesophilic Aeromonas are emerging as important pathogens in humans, causing a variety of extraintestinal and systemic infections, as well as gastrointestinal infections and, at this moment, the Aeromonas infection remain among those infectious disease of potentially serious threat to public health. Recent studies seem to strengthen this hypothesis as the virulence of this genus depends on the bacterial strain, there is a great diversity within the genus and, some virulence factors will probably not be present in these strains or these strains show different mechanism to infect the host than others. In the research carried out, this bacterial group showed the presence of celular surface structures that have been described: polar flagella, several filamentous adhesins types (pili), capsule and “S” layer. However, diverse aspects of the ultrastructure of the cell are still unknow. On the other hand, in previous studies were observed ultrastructurals differences in one Aeromonas strain isolated from asymptomatic patient and, the other one from a patient with diarrhea. This work focuses in the analysis of the diverse ultrastructural aspects of the one Aeromonas strain isolated from a patient with diarrheic syndrome. The investigation was carried out applying the negative stain and transmission electron microscopy. In the analyzed Aeromonas strain, these unusual findings were observed: presence of mesosomes, as well as the existence of two morphotypes having ultrastructural patterns very well defined and different, outer membrane vesicles (OMVs) was seen on the outer surface of the Aeromonas cell. The results obtained show again, the great heterogeneity of this genus, the existence of differences in ultrastructural cell morphology in strains producing diarrheic syndrome and, outline the need to carry out more studies with several Aeromonas strains to determine, the frequency of appearance of the different phenotype and if it has relationship with its pathogenic potential.

Aeromonas spp., Diarrheic Syndrome, Ultrastructural Vision, Outer Membrane Vesicles