Gut microbiota in COVID-19: new insights from inside

Bacillus siamensis Targeted Screening from Highly Colitis-Resistant Pigs Can Alleviate Ulcerative Colitis in Mice

Ulcerative colitis (UC) is often accompanied by intestinal inflammation and disruption of intestinal epithelial structures, which are closely associated with changes in the intestinal microbiota. We previously revealed that Min pigs, a native Chinese breed, are more resistant to dextran sulfate sodium (DSS)-induced colitis than commercial Yorkshire pigs. Characterizing the microbiota in Min pigs would allow identification of the core microbes that confer colitis resistance. By analyzing the microbiota linked to the disease course in Min and Yorkshire pigs, we observed that Bacillus spp. were enriched in Min pigs and positively correlated with pathogen resistance. Using targeted screening, we identified and validated Bacillus siamensis MZ16 from Min pigs as a bacterial species with biofilm formation ability, superior salt and pH tolerance, and antimicrobial characteristics. Subsequently, we administered B. siamensis MZ16 to conventional or microbiota-deficient BALB/c mice with DSS-induced colitis to assess its efficacy in alleviating colitis. B. siamensis MZ16 partially counteracted DSS-induced colitis in conventional mice, but it did not mitigate DSS-induced colitis in microbiota-deficient mice. Further analysis revealed that B. siamensis MZ16 administration improved intestinal ecology and integrity and immunological barrier function in mice. Compared to the DSS-treated mice, mice preadministered B. siamensis MZ16 exhibited improved relative abundance of potentially beneficial microbes (Lactobacillus, Bacillus, Christensenellaceae R7, Ruminococcus, Clostridium, and Eubacterium), reduced relative abundance of pathogenic microbes (Escherichia-Shigella), and maintained colonic OCLN and ZO-1 levels and IgA and SIgA levels. Furthermore, B. siamensis MZ16 reduced proinflammatory cytokine levels by reversing NF-κB and MAPK pathway activation in the DSS group. Overall, B. siamensis MZ16 from Min pigs had beneficial effects on a colitis mouse model by enhancing intestinal barrier functions and reducing inflammation in a gut microbiota-dependent manner.

Exploring the Pathophysiology of Long COVID: The Central Role of Low-Grade Inflammation and Multisystem Involvement

Long COVID (LC), also referred to as Post COVID-19 Condition, Post-Acute Sequelae of SARS-CoV-2 Infection (PASC), and other terms, represents a complex multisystem disease persisting after the acute phase of COVID-19. Characterized by a myriad of symptoms across different organ systems, LC presents significant diagnostic and management challenges. Central to the disorder is the role of low-grade inflammation, a non-classical inflammatory response that contributes to the chronicity and diversity of symptoms observed. This review explores the pathophysiological underpinnings of LC, emphasizing the importance of low-grade inflammation as a core component. By delineating the pathogenetic relationships and clinical manifestations of LC, this article highlights the necessity for an integrated approach that employs both personalized medicine and standardized protocols aimed at mitigating long-term consequences. The insights gained not only enhance our understanding of LC but also inform the development of therapeutic strategies that could be applicable to other chronic conditions with similar pathophysiological features.

Gut Microbiome and Cytokine Profiles in Post-COVID Syndrome

Recent studies highlight the crucial role of the gut microbiome in post-infectious complications, especially in patients recovering from severe COVID-19. Our research aimed to explore the connection between gut microbiome changes and the cytokine profile of patients with post-COVID syndrome. Using 16S rRNA amplicon sequencing, we analyzed the composition of the gut microbiome in 60 COVID-19 patients over the course of one year. We also measured the levels of serum cytokines and chemokines using the Milliplex system. Our results showed that severe SARS-CoV-2 infection cases, especially those complicated by pneumonia, induce a pro-inflammatory microbial milieu with heightened presence of Bacteroides, Faecalibacterium, and Prevotella_9. Furthermore, we found that post-COVID syndrome is characterized by a cross-correlation of various cytokines and chemokines MDC, IL-1b, Fractalkine, TNFa, FGF-2, EGF, IL-1RA, IFN-a2, IL-10, sCD40L, IL-8, Eotaxin, IL-12p40, and MIP-1b as well as a shift in the gut microbiome towards a pro-inflammatory profile. At the functional level, our analysis revealed associations with post-COVID-19 in homolactic fermentation, pentose phosphate, NAD salvage, and flavin biosynthesis. These findings highlight the intricate interplay between the gut microbiota, their metabolites, and systemic cytokines in shaping post-COVID symptoms. Unraveling the gut microbiome's role in post-infectious complications opens avenues for new treatments for those patients with prolonged symptoms.

Microbiota and Immunity during Respiratory Infections: Lung and Gut Affair

Bacterial and viral respiratory tract infections are the most common infectious diseases, leading to worldwide morbidity and mortality. In the past 10 years, the importance of lung microbiota emerged in the context of pulmonary diseases, although the mechanisms by which it impacts the intestinal environment have not yet been fully identified. On the contrary, gut microbial dysbiosis is associated with disease etiology or/and development in the lung. In this review, we present an overview of the lung microbiome modifications occurring during respiratory infections, namely, reduced community diversity and increased microbial burden, and of the downstream consequences on host-pathogen interaction, inflammatory signals, and cytokines production, in turn affecting the disease progression and outcome. Particularly, we focus on the role of the gut-lung bidirectional communication in shaping inflammation and immunity in this context, resuming both animal and human studies. Moreover, we discuss the challenges and possibilities related to novel microbial-based (probiotics and dietary supplementation) and microbial-targeted therapies (antibacterial monoclonal antibodies and bacteriophages), aimed to remodel the composition of resident microbial communities and restore health. Finally, we propose an outlook of some relevant questions in the field to be answered with future research, which may have translational relevance for the prevention and control of respiratory infections.

Alterations in microbiota of patients with COVID-19: implications for therapeutic interventions

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) recently caused a global pandemic, resulting in more than 702 million people being infected and over 6.9 million deaths. Patients with coronavirus disease (COVID-19) may suffer from diarrhea, sleep disorders, depression, and even cognitive impairment, which is associated with long COVID during recovery. However, there remains no consensus on effective treatment methods. Studies have found that patients with COVID-19 have alterations in microbiota and their metabolites, particularly in the gut, which may be involved in the regulation of immune responses. Consumption of probiotics may alleviate the discomfort caused by inflammation and oxidative stress. However, the pathophysiological process underlying the alleviation of COVID-19-related symptoms and complications by targeting the microbiota remains unclear. In the current study, we summarize the latest research and evidence on the COVID-19 pandemic, together with symptoms of SARS-CoV-2 and vaccine use, with a focus on the relationship between microbiota alterations and COVID-19-related symptoms and vaccine use. This work provides evidence that probiotic-based interventions may improve COVID-19 symptoms by regulating gut microbiota and systemic immunity. Probiotics may also be used as adjuvants to improve vaccine efficacy.

The association of three vaccination doses with reduced gastrointestinal symptoms after severe acute respiratory syndrome coronavirus 2 infections in patients with inflammatory bowel disease

Background

The protective efficacy of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccination against the new-onset gastrointestinal (GI) symptoms following COVID-19 infection is critical among patients with inflammatory bowel disease (IBD); however, the optimal protective vaccine dose remains unknown. Therefore, this study aimed to clarify whether there is a correlation between SARS-CoV-2 vaccinations and GI symptoms following Omicron infection in patients with IBD.

Methods

We conducted a multicenter cross-sectional study of IBD patients among three tertiary hospitals in eastern China. Professional physicians collected all data using online questionnaires. The patients were stratified into four groups: patients who were unvaccinated and patients who received one, two, or three vaccination doses. The primary outcome was the presence of any new-onset GI symptoms after SARS-CoV-2 infection before a negative SARS-CoV-2 nucleic acid test or a negative self-testing for antigens.

Results

In total, 536 patients with IBD (175 unvaccinated, 31 vaccinated, 166 vaccinated with two doses, and 164 vaccinated with three doses) reported having COVID-19 infection. Compared with the unvaccinated, the three vaccination doses group was associated with reduced GI symptoms after infection (adjusted odds ratio = 0.56, 95% confidence interval 0.34-0.90, P < 0.05). Reduced diarrhea (adjusted odds ratio = 0.54, 95% confidence interval 0.31-0.92, P < 0.05) and nausea or vomiting (adjusted odds ratio = 0.45, 95% confidence interval 0.21-0.92, P < 0.05) were observed in the three vaccination doses group compared with the unvaccinated group.

Conclusions

In conclusion, in the 536 patients with IBD who reported COVID-19 infection, we found that the three vaccination doses, but not the one or two doses group, were associated with reduced GI symptoms after infection compared with the unvaccinated group.

Repercussion of inflammatory bowel disease on lung homeostasis: The role of photobiomodulation

Inflammatory bowel diseases (IBD) are chronic and multifactorial diseases characterized by dysfunction of the intestinal mucosa and impaired immune response. Data show an important relationship between intestine and respiratory tract. The treatments of IBD are limited. Photobiomodulation (PBM) is an effective anti-inflammatory therapy. Our objective was to evaluate the repercussion of IBD as well as its treatment with PBM on pulmonary homeostasis. Male Wistar rats were submitted to IBD induction by acetic acid and treated or not with PBM. Rats were irradiated with red LED on both right and left sides of the ventral surface and beside the external anal region during 3 consecutive days (wavelenght 660 nm, power 100 mw, total energy 15 J and time of irradiation 150 s per point). Our results showed that IBD altered pulmonary homeostasis, since we observed an increase in the histopathological score, in myeloperoxidase activity (MPO), in mast cell degranulation, and in the release and gene expression of cytokines. We also showed that PBM treatment reduced biomarkers of IBD and reverted all augmented parameters in the lung, restoring its homeostasis. Thus, we confirm experimentally the important gut-lung axis and the role of PBM as a promising therapy.

Lymphocyte and neutrophil count combined with intestinal bacteria abundance predict the severity of COVID-19

IMPORTANCE

The 2019 coronavirus disease (COVID-19) patients had a unique profile of gut bacteria. In this study, we characterized the intestinal bacteria in our COVID-19 cohorts and found that there was an increased incidence of severe cases in COVID-19 patients with decreased lymphocytes and increased neutrophils. Levels of lymphocytes and neutrophils and abundances of intestinal bacteria correlated with the severity of COVID-19.

Gut Microbiome Disruption Following SARS-CoV-2: A Review

COVID-19 has been associated with having a negative impact on patients' gut microbiome during both active disease and in the post-acute phase. In acute COVID-19, rapid alteration of the gut microbiome composition was observed, showing on one side a reduction in beneficial symbionts (e.g., Roseburia, Lachnospiraceae) and on the other side an increase in opportunistic pathogens such as Enterococcus and Proteobacteria. Alpha diversity tends to decrease, especially initially with symptom onset and hospital admission. Although clinical recovery appears to align with improved gut homeostasis, this process could take several weeks, even in mild infections. Moreover, patients with COVID-19 post-acute syndrome showed changes in gut microbiome composition, with specific signatures associated with decreased respiratory function up to 12 months following acute disease. Potential treatments, especially probiotic-based therapy, are under investigation. Open questions remain on the possibility to use gut microbiome data to predict disease progression and on potential confounders that may impair result interpretation (e.g., concomitant therapies in the acute phase; reinfection, vaccines, and occurrence of novel conditions or diseases in the post-acute syndrome). Understanding the relationships between gut microbiome dynamics and disease progression may contribute to better understanding post-COVID syndrome pathogenesis or inform personalized treatment that can affect specific targets or microbiome markers.

Eliminating COVID-19 as the immediate culprit for igniting pancreatitis

The impact of severe acute respiratory syndrome coronavirus 2 infection on the potential development of pancreatitis is a subject of ongoing debate within academic discourse. Establishing a causal link between COVID-19 and pancreatitis may not be fully supported by relying only on retrospective studies or case reports. This study examined the relationship between COVID-19 phenotypes and pancreatitis by Mendelian randomization (MR) method. The identification of instrumental variables (single nucleotide polymorphisms) that exhibit a robust association with the COVID-19 phenotypes was accomplished through a meticulous process of rigorous screening procedures. We included acute pancreatitis and chronic pancreatitis (CP) as the outcomes in the MR analysis, even though no definitive studies exist between COVID-19 and CP. A direct causal relationship between genetically predicted COVID-19 phenotypes and pancreatitis risk cannot be established. There is an ongoing debate over the designation of COVID-19 as a definitive cause of pancreatitis.

The importance of the gut microbiome in the pathogenesis and transmission of SARS-CoV-2

Zhou et al. study nicely traces a significant topic in COVID-19 infection: the persistence of the virus within the intestinal tract. Many pathological mechanisms have been noted in the current literature about the mode of infection and propagation of SARS-CoV-2 in the human body. Nevertheless, there are still many concerns about this: only some things seem well understood. We present a different point of view by illustrating the importance of the gut microbiome in the pathogenesis of COVID-19 disorders.