Could Aeromonas spp. be considered a vector of resistance genes from the environment to human intestinal flora?

Antibiotic resistant bacteria and antibiotic resistance genes cause increasing problems in clinical setting and are considered emerging environmental contaminants. In the environment, antibiotic resistant bacteria may be inactivated but their resistance determinants may become part of the environmental gene pool and may move back to human and animal intestinal flora via food and drinking water. In order to assess the role of Aeromonas spp. in the flow of resistant determinants, we analyzed by resistance profiles, plasmidic and integrons content and characterization, 231 Aeromonas spp. and 250 Fecal Coliforms isolated from different aquatic environments. Resistance patterns could be related to both the presence of multiple plasmids and to the origin of the strains. The 31.7% of the plasmids carried by the Aeromonas strains were mobilizable as assess by dot-blot of MOB-subfamily covering the BHR (Broad Host Range) incompatibility groups. The majority (75%) of the Class 1 integrons were chromosomally locate and were found in the 27.7% of the Aeromonas spp. tested. The number and type of resistance genes identified so far on Aeromonas spp. Support the hypothesis of considering these bacteria as a "reservoir" of resistance genes. The capability of some Aeromonas strains to transfer their resistance to Fecal Coliform has been demonstrated, thus allowing to assert its role as a “vector” of resistance genes to members of the human intestinal flora.