Murine response to the opportunistic bacterium Pseudomonas aeruginosa infection in gut dysbiosis caused by 5-fluorouracil chemotherapy-induced mucositis.

AIMS: This manuscript aims to explain the relationship between mucositis caused by 5-FU over gut bacterial species and susceptibility to opportunistic infection caused by P. aeruginosa. MAIN METHODS: BALB/c mice were intraperitoneally treated with PBS or 5-FU. Bodyweight and faecal consistency were checked daily. Mice faecal DNA was extracted, and bacterial phylogenetic groups were analysed using qPCR or high-throughput sequencing. Immunofluorescence was used to evaluate BMDM activation by mice-treated faecal content. Mice were challenged intratracheally with virulent P. aeruginosa, and the CFU and histology were analysed. Faecal microbiota were transplanted to evaluate the gut microbiota and resistance to pulmonary P. aeruginosa recovery. KEY FINDINGS: The animals treated with 5-FU presented mucositis with great weight loss, altered faecal consistency, bacterial gut dysbiosis and histological changes in the intestinal mucosa. Mice under 5-FU treatment were more susceptible to lung infection by the bacteria P. aeruginosa and had more extensive tissue damage during their lung infection with greater pro-inflammatory gene expression. It was observed that the mucositis remained in the groups with 5-FU even with the FMT. The results caused by mucositis in animals that received allogeneic FMT were reversed, however, with a decrease in P. aeruginosa susceptibility in animals treated with 5-FU and allogeneic FMT compared to animals treated with 5-FU and autologous FMT. SIGNIFICANCE: Treatment with 5-FU in a murine model makes it more susceptible to pulmonary infection by the bacterium P. aeruginosa, FMT offers an opportunity to protect against this susceptibility to infection.

Akkermansia muciniphila and Gut Immune System: A Good Friendship That Attenuates Inflammatory Bowel Disease, Obesity, and Diabetes.

Akkermansia muciniphila is a Gram-negative anaerobic mucus-layer-degrading bacterium that colonizes the intestinal mucosa of humans and rodents. Metagenomic data have shown an inverse correlation between the abundance of A. muciniphila and diseases such as inflammatory bowel disease (IBD), obesity, and diabetes. Thus, in recent decades, the potential of this bacterium as an immunomodulatory probiotic for autoimmune and chronic inflammatory diseases has been explored in experimental models. Corroborating these human correlation data, it has been reported that A. muciniphila slows down the development and progression of diabetes, obesity, and IBD in mice. Consequently, clinical studies with obese and diabetic patients are being performed, and the preliminary results are very promising. Therefore, this mini review highlights the main findings regarding the beneficial roles of A. muciniphila and its action mechanisms in autoimmune and chronic inflammatory diseases.

The role of IL-10 in immune responses against Pseudomonas aeruginosa during acute lung infection.

Pseudomonas aeruginosa is considered an opportunistic pathogen of great clinical importance. The clearance of this bacterium occurs through recognition of the pathogen by innate immune system receptors, leading to a lung inflammatory response. However, this response must be controlled via immunoregulatory pathways. In this study, we evaluate the role of endogenous murine IL-10 after acute infection with the virulent strain P. aeruginosa PA14. To assess the role of IL-10, intratracheal infection with the PA14 strain was performed in C57BL/6 or IL-10 KO mice. The PA14 strain was recovered in both types of animals, although IL-10 KO mice presented a higher number of viable bacteria in the lung when compared to the C57BL/6 group. Histopathological and stereological analyses showed that IL-10 KO mice had higher tissue damage and inflammatory infiltrate when compared to control animals. The activity of MMP-9 but not MMP-2, as well as IL-6 and TNF-α expression, were augmented in the lungs of infected animals and was much more evident in IL-10 KO animals when compared to the other analyzed groups. This work indicates that endogenous IL-10 control P. aeruginosa infection, the expression of pro-inflammatory genes, MMP-9 activity and histopathological processes of the infectious process in question.

Vancomycin-induced gut dysbiosis during Pseudomonas aeruginosa pulmonary infection in a mice model.

Pseudomonas aeruginosa is one of the most common opportunistic pathogens causing respiratory infections in hospitals. Vancomycin, the antimicrobial agent usually used to treat bacterial nosocomial infections, is associated with gut dysbiosis. As a lung-gut immunologic axis has been described, this study aimed to evaluate both the immunologic and histopathologic effects on the lungs and the large intestine resulting from vancomycin-induced gut dysbiosis in the P. aeruginosa pneumonia murine model. Metagenomic analysis demonstrated that vancomycin-induced gut dysbiosis resulted in higher Proteobacteria and lower Bacteroidetes populations in feces. Given that gut dysbiosis could augment the proinflammatory status of the intestines leading to a variety of acute inflammatory diseases, bone marrow-derived macrophages were stimulated with cecal content from dysbiotic mice showing a higher expression of proinflammatory cytokines and lower expression of IL-10. Dysbiotic mice showed higher levels of viable bacteria in the lungs and spleen when acutely infected with P. aeruginosa, with more lung and cecal damage and increased IL-10 expression in bronchoalveolar lavage. The susceptible and tissue damage phenotype was reversed when dysbiotic mice received fecal microbiota transplantation. In spite of higher recruitment of CD11b+ cells in the lungs, there was no higher CD80+ expression, DC+ cell amounts or proinflammatory cytokine expression. Taken together, our results indicate that the bacterial community found in vancomycin-induced dysbiosis dysregulates the gut inflammatory status, influencing the lung-gut immunologic axis to favor increased opportunistic infections, for example, by P. aeruginosa.