Akkermansia muciniphila Associated with Improved Linear Growth among Young Children, Democratic Republic of the Congo

To investigate the association between enteric pathogens, fecal microbes, and child growth, we conducted a prospective cohort study of 236 children <5 years of age in rural eastern Democratic Republic of the Congo. We analyzed baseline fecal specimens by quantitative PCR and measured child height and weight at baseline and growth at a 6-month follow-up. At baseline, 66% (156/236) of children had >3 pathogens in their feces. We observed larger increases in height-for-age-z-scores from baseline to the 6-month follow-up among children with Akkermansia muciniphila in their feces (coefficient 0.02 [95% CI 0.0001-0.04]; p = 0.04). Children with Cryptosporidium in their feces had larger declines in weight-for-height/length z-scores from baseline to the 6-month follow-up (coefficient -0.03 [95% CI -0.05 to -0.005]; p = 0.02). Our study showed high prevalence of enteric pathogens among this pediatric cohort and suggests A. muciniphila can potentially serve as a probiotic to improve child growth.

The Increased Abundance of Commensal Microbes Decreases Drosophila melanogaster Lifespan through an Age-Related Intestinal Barrier Dysfunction

BACKGROUND

Commensal microbiota live in their host with a symbiotic relationship that affects the host's health and physiology. Many studies showed that microbial load and composition were changed by aging and observed that increasing the abundance and changing the composition of commensal microbes had detrimental effects on host lifespan. We hypothesized that dysbiosis of the intestinal microbiota leads to systemic effects in aging flies as a result of the increased intestinal permeability.

METHODS

We used the fruit fly, Drosophila melanogaster, laboratory strains w¹¹¹⁸, as a model system with many advantages for microbe-host studies.

RESULTS

The incidence of intestinal dysfunction was increased with age, and intestinal dysfunction increased the permeability of the fly intestine to resident microbes. The lifespan of flies with an intestinal barrier dysfunction was increased by removal of the microbes. Interestingly, some bacteria were also found in the hemolymph of flies with intestinal barrier dysfunction.

CONCLUSION

Our findings suggest the possibility that, as the host ages, there is an increase in intestinal permeability, which leads to an increased intestinal microbial load and a reduction in the host lifespan. Our data therefore indicate a connection between commensal microbes and host lifespan.

Escherichia coli Shiga Toxins and Gut Microbiota Interactions

Escherichia coli (EHEC) and Shigella dysenteriae serotype 1 are enterohemorrhagic bacteria that induce hemorrhagic colitis. This, in turn, may result in potentially lethal complications, such as hemolytic uremic syndrome (HUS), which is characterized by thrombocytopenia, acute renal failure, and neurological abnormalities. Both species of bacteria produce Shiga toxins (Stxs), a phage-encoded exotoxin inhibiting protein synthesis in host cells that are primarily responsible for bacterial virulence. Although most studies have focused on the pathogenic roles of Stxs as harmful substances capable of inducing cell death and as proinflammatory factors that sensitize the host target organs to damage, less is known about the interface between the commensalism of bacterial communities and the pathogenicity of the toxins. The gut contains more species of bacteria than any other organ, providing pathogenic bacteria that colonize the gut with a greater number of opportunities to encounter other bacterial species. Notably, the presence in the intestines of pathogenic EHEC producing Stxs associated with severe illness may have compounding effects on the diversity of the indigenous bacteria and bacterial communities in the gut. The present review focuses on studies describing the roles of Stxs in the complex interactions between pathogenic Shiga toxin-producing E. coli, the resident microbiome, and host tissues. The determination of these interactions may provide insights into the unresolved issues regarding these pathogens.

The Skin Microbiota: Balancing Risk and Reward

The skin microbiome is an ecosystem comprised of a multitude of microbial species interacting with their surroundings, including other microbes and host epithelial and immune cells. These interactions are the basis of important roles within the skin microbiome that provide benefit to the host, boosting multiple aspects of barrier function, a critical function of this essential organ. However, with reward always comes risk; resident skin microbes function in a context-dependent manner, set on the backdrop of a dynamic host and microbial milieu. Here, we discuss the reward of hosting a microbial ecosystem on the skin, including protection from pathogens and tuning of the skin microenvironment. We also give consideration to how these skin residents, often termed "commensals" can cause disorder, damage, and promote skin disease.

The commensal consortium of the gut microbiome is associated with favorable responses to anti-programmed death protein 1 (PD-1) therapy in thoracic neoplasms

OBJECTIVE

Immune checkpoint inhibitors have revolutionized cancer therapy for multiple types of solid tumors, but as expected, a large percentage of patients do not show durable responses. Biomarkers that can predict clinical responses to immunotherapies at diagnosis are therefore urgently needed. Herein, we determined the associations between baseline gut commensal microbes and the clinical treatment efficiencies of patients with thoracic neoplasms during anti-programmed death protein 1 (PD-1) therapy.

METHODS

Forty-two patients with advanced thoracic carcinoma who received anti-PD-1 treatment were enrolled in the study. Baseline and time-serial stool samples were analyzed using 16S ribosomal RNA gene sequencing. Tumor responses, patient progression-free survival, and overall survival were used to measure clinical outcomes.

RESULTS

The diversities of the baseline gut microbiota were similar between responders (n = 23) and nonresponders (n = 19). The relative abundances of the Akkermansiaceae, Enterococcaceae, Enterobacteriaceae, Carnobacteriaceae and Clostridiales Family XI bacterial families were significantly higher in the responder group. These 5 bacterial families acted as a commensal consortium and better stratified patients according to clinical responses (P = 0.014). Patients with a higher abundance of commensal microbes had prolonged PFS (P = 0.00016). Using multivariable analysis, the abundance of the commensal consortium was identified as an independent predictor of anti-PD-1 immunotherapy in thoracic neoplasms (hazard ratio: 0.17; 95% confidence interval: 0.05-0.55; P = 0.003).

CONCLUSIONS

Baseline gut microbiota may have a critical impact on anti-PD-1 treatment in thoracic neoplasms. The abundance of gut commensal microbes at diagnosis might be useful for the early prediction of anti-PD-1 immunotherapy responses.

Role of Commensal Microbes in the γ-Ray Irradiation-Induced Physiological Changes in Drosophila melanogaster

Ionizing radiation induces biological/physiological changes and affects commensal microbes, but few studies have examined the relationship between the physiological changes induced by irradiation and commensal microbes. This study investigated the role of commensal microbes in the γ-ray irradiation-induced physiological changes in Drosophila melanogaster. The bacterial load was increased in 5 Gy irradiated flies, but irradiation decreased the number of operational taxonomic units. The mean lifespan of conventional flies showed no significant change by irradiation, whereas that of axenic flies was negatively correlated with the radiation dose. γ-Ray irradiation did not change the average number of eggs in both conventional and axenic flies. Locomotion of conventional flies was decreased after 5 Gy radiation exposure, whereas no significant change in locomotion activity was detected in axenic flies after irradiation. γ-Ray irradiation increased the generation of reactive oxygen species in both conventional and axenic flies, but the increase was higher in axenic flies. Similarly, the amounts of mitochondria were increased in irradiated axenic flies but not in conventional flies. These results suggest that axenic flies are more sensitive in their mitochondrial responses to radiation than conventional flies, and increased sensitivity leads to a reduced lifespan and other physiological changes in axenic flies.

Commensal Fungi Recapitulate the Protective Benefits of Intestinal Bacteria

Commensal intestinal microbes are collectively beneficial in preventing local tissue injury and augmenting systemic antimicrobial immunity. However, given the near-exclusive focus on bacterial species in establishing these protective benefits, the contributions of other types of commensal microbes remain poorly defined. Here, we show that commensal fungi can functionally replace intestinal bacteria by conferring protection against injury to mucosal tissues and positively calibrating the responsiveness of circulating immune cells. Susceptibility to colitis and influenza A virus infection occurring upon commensal bacteria eradication is efficiently overturned by mono-colonization with either Candida albicans or Saccharomyces cerevisiae. The protective benefits of commensal fungi are mediated by mannans, a highly conserved component of fungal cell walls, since intestinal stimulation with this moiety alone overrides disease susceptibility in mice depleted of commensal bacteria. Thus, commensal enteric fungi safeguard local and systemic immunity by providing tonic microbial stimulation that can functionally replace intestinal bacteria.