Epidemiology and pathogenic characterization of species of the genus aeromonas
- Autores: Ana Fernández Bravo
- Directores de la Tesis: María José Figueras Salvat (dir. tes.)
- Lectura: En la Universitat Rovira i Virgili ( España ) en 2019
- Idioma: español
- Tribunal Calificador de la Tesis: Antonio J. Martínez Murcia (presid.), Loida López Fernández (secret.), Mark R. Liles (voc.)
- Programa de doctorado: Programa de Doctorado en Biomedicina por la Universidad Rovira i Virgili
- Materias:
- Enlaces
- Tesis en acceso abierto en: TDX
- Resumen
The genus Aeromonas includes more than 32 species, some of which are distributed in the environment and are considered to be indigenous to aquatic systems.Nowadays, the water is a limited resource and for this reason different methods of water treatment have been developed, included the treatment of the wastewater to generate reclaimed water that usually is used for irrigation. For this reason, we continue studying the presence of Aeromonas in water by qPCR, in addition to evaluating the skimmed milk flocculation method used for virus detection. The results demonstrated that the skimmed milk flocculation it seems to be a good method for the detection of Aeromonas, detecting these bacteria in 100% of the samples.
The Aeromonas is an emerging pathogen that cause a wide spectrum of diseases, mainly gastroenteritis, wound infections and bacteremia/septicemia. Recent publications show that 96.5% of the strains associated to clinical cases correspond to 4 species: Aeromonas caviae (29.9%), Aeromonas dhakensis (26.3%), Aeromonas veronii (24.8%) and Aeromonas hydrophila (15.5%), however other less prevalent species, such as A. salmonicida, associated usually with the fish diseases, are also described from clinical samples. To evaluate the pathogenicity of this species an in vivo model was used, and a comparison of the genomes was performed to understanding this pathogenicity. The results confirmed that A. salmonicida can infect mammals with different levels of pathogenicity and this could be associated with the presence of several genes involved in the virulence.
Considering the increase of infections by Aeromonas in recent years, different collaborations with university hospitals have been carried out to investigated different cases, including the possible confusions between Aeromonas and Vibrio previously described. In this cases, a comparation with the phenotypic method API 20E and the sequencing of the rpoD gene was performed, showing the limitation of the API 20E for the identification of Aeromonas and Vibrio. Also, a review of different studies was carry out to alert the importance of these emerging pathogens for the clinicians. In these studies, we also evaluated the MALDI-TOF system for identification. Additionally, another a study with strains isolated from fish was performed to evaluate this system, demonstrating that the MALDI-TOF was not precise due to the deficiencies in the database.
The use of genomes, their comparison and the development of new bioinformatic tools, proved to be useful to understand the potential function of A. lusitana. This species is recently described from water and vegetables in Portugal, and the draft genome is a valuable addition to the genomic database to contribute to the understanding of the role of this species in the environment. Also, to reinforce the data obtained in the genome, the presence of the virulence factors and the phenotypic characteristics were evaluated. This study confirms that the biochemical characteristics and the virulence pattern profile are complex in the genus Aeromonas The virulence of Aeromonas is multifactorial. For this reason, in this doctoral thesis the metallochaperone HypA previously described with role in tolerance to stomach acid in other pathogens was characterized using an in vitro model. The results showed an upregulation of this metallochaperone after acid exposure and after macrophage infection, suggesting that the HypA contributes in the acidic survival, as well as in the defense against ROS produced by macrophages in the phagocytic process. Moreover, recently the mixed infections has been described that occur in 5-10% of the infections. In our study, we evaluated the role of the ExoA toxin and the type VI secretion system (T6SS) in mixed infections that progress in a necrotizing fasciitis using several mutant strains. The results suggested that ExoA plays a role in bacterial dissemination and the T6SS could be involved in the antagonistic effect between both strains, generating a different course of the disease in comparison with the single strain infection. Finally, a study of the defense of human monocytes against Aeromonas was performed to clarify if exist a species specific immune response that explain the different prevalent of the species in the humans infections. For this, we studied the expression of 11 immune-related genes. Our data demonstrated that the most prevalent clinical species activate a higher immune response than the less prevalent species, probably this result is associated with a cytokines storm that is a systemic inflammatory response syndrome that increase the severity of the infections.
