Quorum sensing modulates bacterial virulence and colonization dynamics of the gastrointestinal pathogen Citrobacter rodentium.

Quorum Sensing (QS) is a form of cell-to-cell communication that enables bacteria to modify behavior according to their population density. While QS has been proposed as a potential intervention against pathogen infection, QS-mediated communication within the mammalian digestive tract remains understudied. Using an LC-MS/MS approach, we discovered that Citrobacter rodentium, a natural murine pathogen used to model human infection by pathogenic Escherichia coli, utilizes the CroIR system to produce three QS-molecules. We then profiled their accumulation both in vitro and across different gastrointestinal sites over the course of infection. Importantly, we found that in the absence of QS capabilities the virulence of C. rodentium is enhanced. This highlights the role of QS as an effective mechanism to regulate virulence according to the pathogen's spatio-temporal context to optimize colonization and transmission success. These results also demonstrate that inhibiting QS may not always be an effective strategy for the control of virulence.

Gut microbiota, malnutrition, and immunity: COVID-19's confounding triad.

The coronavirus disease has swept the world, bringing scientists from multiple disciplines together to work on a focused cause. In this forum, we discuss different roles that microbiota, malnutrition, and immunity have on severity of coronavirus disease and the importance of studying them from a gut-systemic perspective using multi-omics approaches.

Type VI secretion systems of pathogenic and commensal bacteria mediate niche occupancy in the gut.

The type VI secretion system (T6SS) is a contractile nanomachine widely distributed among pathogenic and commensal Gram-negative bacteria. The T6SS is used for inter-bacterial competition to directly kill competing species; however, its importance during bacterial infection in vivo remains poorly understood. We report that the murine pathogen Citrobacter rodentium, used as a model for human pathogenic Escherichia coli, harbors two functional T6SSs. C. rodentium employs its T6SS-1 to colonize the murine gastrointestinal tract by targeting commensal Enterobacteriaceae. We identify VgrG1 as a C. rodentium T6SS antibacterial effector, which exhibits toxicity in E. coli. Conversely, commensal prey species E. coli Mt1B1 employs two T6SSs of its own to counter C. rodentium colonization. Collectively, these data demonstrate that the T6SS is a potent weapon during bacterial competition and is used by both invading pathogens and resident microbiota to fight for a niche in the hostile gut environment.

Nonalcoholic Fatty Liver Disease and the Gut-Liver Axis: Exploring an Undernutrition Perspective.

Nonalcoholic fatty liver disease (NAFLD) is a chronic condition affecting one quarter of the global population. Although primarily linked to obesity and metabolic syndrome, undernutrition and the altered (dysbiotic) gut microbiome influence NAFLD progression. Both undernutrition and NAFLD prevalence are predicted to considerably increase, but how the undernourished gut microbiome contributes to hepatic pathophysiology remains far less studied. Here, we present undernutrition conditions with fatty liver features, including kwashiorkor and micronutrient deficiency. We then review the gut microbiota-liver axis, highlighting key pathways linked to NAFLD progression within both overnutrition and undernutrition. To conclude, we identify challenges and collaborative possibilities of emerging multiomic research addressing the pathology and treatment of undernourished NAFLD.

Associations between Both Lignan and Yogurt Consumption and Cardiovascular Risk Parameters in an Elderly Population: Observations from a Cross-Sectional Approach in the PREDIMED Study.

BACKGROUND: The study of dietary patterns is gaining interest. Although the health benefits of yogurt and lignans have been investigated separately, to our knowledge there are no studies on their associative effects. OBJECTIVE: The aim of this study was to evaluate a possible association between yogurt and lignans using biomarkers of cardiovascular disease risk in an elderly population. DESIGN: We conducted a cross-sectional analysis of the association between baseline dietary information and cardiovascular risk parameters using food frequency questionnaires. PARTICIPANTS: We enrolled 7,169 Spanish participants of the PREDIMED (Prevención con Dieta Mediterránea) study (elderly men and women at high cardiovascular risk) from June 2003 to June 2009. MAIN OUTCOME MEASURES: Cardiovascular risk parameters, including cholesterol, triglycerides, glucose, body mass index, weight, waist circumference, and blood pressure were measured. STATISTICAL ANALYSIS: General linear models were used to assess the relationship between categorical variables (yogurt, total dairy intake, lignans, and yogurt plus lignans) and cardiovascular risk parameters. RESULTS: The consumption of either yogurt or lignans seems to have beneficial effects on human health, but the consumption of both showed greater improvement in some cardiovascular health parameters. Indeed, participants with a higher consumption of both yogurt and lignans showed lower total cholesterol (estimated ß-coefficients=-6.18; P=0.001) and low-density lipoprotein cholesterol levels (ß=-4.92; P=0.005). In contrast, participants with lower yogurt and lignan consumption had a higher body mass index (ß=0.28; P=0.007) and weight (ß=1.20; P=0.008). CONCLUSIONS: High lignan and yogurt consumption is associated with a better cardiovascular risk parameters profile in an elderly Mediterranean population. Further research is warranted to determine the mechanisms and consequences of this potential effect.

Safe Reduction in CD4 Cell Count Monitoring in Stable, Virally Suppressed Patients With HIV Infection or HIV/Hepatitis C Virus Coinfection.

BACKGROUND: It has been suggested that routine CD4 cell count monitoring in human immunodeficiency virus (HIV)-monoinfected patients with suppressed viral loads and CD4 cell counts >300 cell/µL could be reduced to annual. HIV/hepatitis C virus (HCV) coinfection is frequent, but evidence supporting similar reductions in CD4 cell count monitoring is lacking for this population. We determined whether CD4 cell count monitoring could be reduced in monoinfected and coinfected patients by estimating the probability of maintaining CD4 cell counts ≥200 cells/µL during continuous HIV suppression. METHODS: The PISCIS Cohort study included data from 14 539 patients aged ≥16 years from 10 hospitals in Catalonia and 2 in the Balearic Islands (Spain) since January 1998. All patients who had at least one period of 6 months of continuous HIV suppression were included in this analysis. Cumulative probabilities with 95% confidence intervals were calculated using the Kaplan-Meier estimator stratified by the initial CD4 cell count at the period of continuous suppression initiation. RESULTS: A total of 8695 patients were included. CD4 cell counts fell to <200 cells/µL in 7.4% patients, and the proportion was lower in patients with an initial count >350 cells/µL (1.8%) and higher in those with an initial count of 200-249 cells/µL (23.1%). CD4 cell counts fell to <200 cells/µL in 5.7% of monoinfected and 11.1% of coinfected patients. Of monoinfected patients with an initial CD4 cell count of 300-349 cells/µL, 95.6% maintained counts ≥200 cells/µL. In the coinfected group with the same initial count, this rate was lower, but 97.6% of coinfected patients with initial counts >350 cells/µL maintained counts ≥200 cells/µL. CONCLUSIONS: From our data, it can be inferred that CD4 cell count monitoring can be safely performed annually in HIV-monoinfected patients with CD4 cell counts >300 cells/µL and HIV/HCV-coinfected patients with counts >350 cells/µL.