Efeito dos metabólitos de triptofano provenientes da microbiota indígena sobre a virulência de isolados clínicos de Pseudomonas aeruginosa

Abstract

Patients developing treatment in an Intensive Care Unit (ICU) and immunocompromised are often victims of opportunistic infections, such as respiratory and urinary tract infections. Furthermore, the long course of antibiotic therapy contributes to the spread of resistance between species and to deleterious impacts on the beneficial microbiome. The disbiotic effect, whether due to changes in microbial diversity or metabolite production, can favor host colonization by pathogens. It is known, for example, that indole, a product of the metabolism of the essential amino acid tryptophan by the indigenous microbiota, is able to modulate the expression and activity of virulence factors in Pseudomonas aeruginosa in vitro, acting in the control of experimental infection by this bacterium. P. aeruginosa is a Gram-negative opportunistic pathogen and one of the main agents of pneumonia in the hospital environment, responsible for high rates of morbidity and mortality. Due to its resistant multidrug character and its diversity in pathogenicity factors, it is necessary to search for molecules with potential anti-virulence activity. In this sense, the aim of this study was to evaluate the effect of indole and other tryptophan metabolites from the indigenous microbiota on the virulence of clinical isolates of P. aeruginosa. For this, in vitro tests of motility, biofilm production and quantification of pyocyanin and pyoverdine were performed using strains PAO1, PA103, PA14 and clinical isolates obtained from Hospital Risoleta Tolentino Neves. Furthermore, we investigated the expression of genes involved in virulence by P. aeruginosa in the presence or absence of tryptophan metabolites and verified the effect of P. aeruginosa exposure to metabolites in the interaction with murine macrophages in vitro, and during experimental pulmonary infection in mice. The studied metabolites reduced the motility capacity, as well as the production of the pigments pyocyanin and pioverdine. On the other hand, indole and indoleacetic acid (IAce) favored biofilm formation by P. aeruginosa, and the indole effect was more pronounced. Furthermore, we demonstrated that these metabolites also alter the course of lung infection in an experimental murine model, since animals infected with the bacteria grown in the presence of indole showed greater weight loss and, consequently, a higher fatality rate. Furthermore, we found that the animals that received the bacteria grown in the IAce had a lower lethality rate compared to the control group, despite having a higher bacterial load in the bronchoalveolar lavage. The analysis of clinical isolates of P. aeruginosa confirmed the high phenotypic diversity of this pathogen, which reflected in varied effects of indole and IAce. Our results demonstrated that tryptophan products by the metabolism of the intestinal microbiota are able to change the virulence profile both in laboratory strains and in clinical isolates of Pseudomonas aeruginosa.