Epidemiology of the genus Aeromonas in Spanish hospitals: pathogenic characterization of two new species

Identifier:  TFG:2976

Handle: https://hdl.handle.net/20.500.11797/TFG2976

Authors:  Berges Buxeda, Marcos Joaquín

Abstract:
Aeromonas genus belongs to the family Aeromonadeceae. The microorganisms included in this genus are characterized by being Gram-negative bacilli widely distributed in aquatic environments and equally isolable in various foods, some animals and in infectious processes in humans. Some Aeromonas species are considered emerging opportunistic pathogens, because they are isolated as etiological agents in various infectious processes, mainly gastroenteritis, septicemia and wound infection. The main objective of this work is contributing to the knowledge of the epidemiology and pathogenicity of this genus. Collaborations with several Spanish hospitals have shown that, due to deficiencies in their databases, the use of MALDI-TOF mass spectrometry is an imprecise method for identifying Aeromonas from clinical samples. However, the use of rpoD gene sequencing has been shown to be useful for bacterial identification at the species level. The strains identified as Aeromonas were mostly recovered from feces samples (68%). The rest came from blood and wound samples, mainly. Out of the reidentified strains, the most abundant species turned out to be Aeromonas caviae, which was expected since it is the most prevalent in feces. Two new species have also been characterized in this study: Aeromonas enterica and Aeromonas intestinalis. Both generated in vitro results similar to those obtained for clinically low prevalent species, which could explain their low prevalence level. Furthermore, the most prevalent species were shown to overactivate the immune system, causing what is known as “cytokine storm”, while these two new species did not overexpress the proinflammatory cytokine TNF-α, indicating a possible low virulence on their part. However, further studies would be necessary to clarify this claim. We can conclude that Aeromonas is a genre increasingly studied in clinics and, therefore, reliable identification methods are needed to know the real prevalence of its different species. Likewise, it is necessary to carry out more in vitro and in vivo studies to evaluate the interaction of these new species with the host. Finally, and considering all the cases analyzed, it is evident that the genus Aeromonas should be recognized as a true pathogen.