An Aniline-Substituted Bile Salt Analog Protects both Mice and Hamsters from Multiple Clostridioides difficile Strains.

Clostridioides difficile infection (CDI) is the major identifiable cause of antibiotic-associated diarrhea. The emergence of hypervirulent C. difficile strains has led to increases in both hospital- and community-acquired CDI. Furthermore, the rate of CDI relapse from hypervirulent strains can reach up to 25%. Thus, standard treatments are rendered less effective, making new methods of prevention and treatment more critical. Previously, the bile salt analog CamSA (cholic acid substituted with m-aminosulfonic acid) was shown to inhibit spore germination in vitro and protect mice and hamsters from C. difficile strain 630. Here, we show that CamSA was less active in preventing spore germination by other C. difficile ribotypes, including the hypervirulent strain R20291. The strain-specific in vitro germination activity of CamSA correlated with its ability to prevent CDI in mice. Additional bile salt analogs were screened for in vitro germination inhibition activity against strain R20291, and the most active compounds were tested against other strains. An aniline-substituted bile salt analog, CaPA (cholic acid substituted with phenylamine), was found to be a better antigerminant than CamSA against eight different C. difficile strains. In addition, CaPA was capable of reducing, delaying, or preventing murine CDI signs with all strains tested. CaPA-treated mice showed no obvious toxicity and showed minor effects on their gut microbiome. CaPA's efficacy was further confirmed by its ability to prevent CDI in hamsters infected with strain 630. These data suggest that C. difficile spores respond to germination inhibitors in a strain-dependent manner. However, careful screening can identify antigerminants with broad CDI prophylaxis activity.

Active free secretory component and secretory IgA in human milk: do maternal vaccination, allergy, infection, mode of delivery, nutrition and active lifestyle change their concentrations?

BACKGROUND: Free secretory component (free SC) in human milk is a critical constituent of secretory IgA (SIgA) for immune exclusion, but its concentration in human milk is unknown. To evaluate the relationship between free SC and SIgA, the influence of maternal factors (vaccination during pregnancy, allergy, previous infections, nutrition, mode of delivery and active lifestyle) on the concentrations of those secretory immune components in human milk was investigated. METHODS: Concentration of active free SC and SIgA in 124 milk samples from 91 mothers were measured via ELISA. RESULTS: Free SC in milk from Tdap-vaccinated mothers was lower than the Tdap-flu-vaccinated, flu-vaccinated or Rhogam-vaccinated mothers. Free SC in mothers who had a cesarean delivery was higher than mothers who had a vaginal delivery. Free SC in the nonallergic group was higher than the allergic group. Free SC was higher in mothers who rarely/never eat junk food, than in mothers who always/frequently eat junk food. Free SC also was higher in the moderate exercise group (active lifestyle) compared with the group who rarely/never exercise (sedentary lifestyle). Free SC in human milk was not affected by previous maternal infection or probiotic supplementation whereas SIgA was not changed by all investigated maternal factors. CONCLUSION: This study suggests that active free SC is more impacted by maternal factors than active SIgA in human milk. IMPACT: Active free secretory component (free SC) is more impacted by maternal factors than active secretory IgA (SIgA) in human milk. Vaccination during pregnancy, allergy, nutrition, type of delivery and active lifestyle affect the secretion of free SC in human milk, but not SIgA secretion. Free SC in human milk is a critical constituent of secretory IgA (SIgA) for immune exclusion against pathogens and its active concentration in milk strongly varies between mothers, partially due to their specific maternal background.

Difference in levels of SARS-CoV-2 S1 and S2 subunits- and nucleocapsid protein-reactive SIgM/IgM, IgG and SIgA/IgA antibodies in human milk.

OBJECTIVE: This study evaluated the presence and the levels of antibodies reactive to SARS-CoV-2 S1 and S2 subunits (S1 + S2), and nucleocapsid protein. STUDY DESIGN: The levels of SARS-CoV-2 S1 + S2- and nucleocapsid-reactive SIgM/IgM, IgG and SIgA/IgA were measured in human milk samples from 41 women during the COVID-19 pandemic (2020-HM) and from 16 women 2 years prior to the outbreak (2018-HM). RESULTS: SARS-CoV-2 S1 + S2-reactive SIgA/IgA, SIgM/IgM and IgG were detected in 97.6%, 68.3% and 58.5% in human milk whereas nucleocapsid-reactive antibodies were detected in 56.4%, 87.2% and 46.2%, respectively. S1 + S2-reactive IgG was higher in milk from women that had symptoms of viral respiratory infection(s) during the last year than in milk from women without symptom. S1 + S2- and nucleocapsid-reactive IgG were higher in the 2020-HM group compared to the 2018-HM group. CONCLUSIONS: The presence of SARS-CoV-2-reactive antibodies in human milk could provide passive immunity to breastfed infants and protect them against COVID-19 diseases.

A High-Fat/High-Protein, Atkins-Type Diet Exacerbates Clostridioides (Clostridium) difficile Infection in Mice, whereas a High-Carbohydrate Diet Protects.

Clostridioides difficile (formerly Clostridium difficile) infection (CDI) can result from the disruption of the resident gut microbiota. Western diets and popular weight-loss diets drive large changes in the gut microbiome; however, the literature is conflicted with regard to the effect of diet on CDI. Using the hypervirulent strain C. difficile R20291 (RT027) in a mouse model of antibiotic-induced CDI, we assessed disease outcome and microbial community dynamics in mice fed two high-fat diets in comparison with a high-carbohydrate diet and a standard rodent diet. The two high-fat diets exacerbated CDI, with a high-fat/high-protein, Atkins-like diet leading to severe CDI and 100% mortality and a high-fat/low-protein, medium-chain-triglyceride (MCT)-like diet inducing highly variable CDI outcomes. In contrast, mice fed a high-carbohydrate diet were protected from CDI, despite the high levels of refined carbohydrate and low levels of fiber in the diet. A total of 28 members of the Lachnospiraceae and Ruminococcaceae decreased in abundance due to diet and/or antibiotic treatment; these organisms may compete with C. difficile for amino acids and protect healthy animals from CDI in the absence of antibiotics. Together, these data suggest that antibiotic treatment might lead to loss of C. difficile competitors and create a favorable environment for C. difficile proliferation and virulence with effects that are intensified by high-fat/high-protein diets; in contrast, high-carbohydrate diets might be protective regardless of the source of carbohydrate or of antibiotic-driven loss of C. difficile competitors.IMPORTANCE The role of Western and weight-loss diets with extreme macronutrient composition in the risk and progression of CDI is poorly understood. In a longitudinal study, we showed that a high-fat/high-protein, Atkins-type diet greatly exacerbated antibiotic-induced CDI, whereas a high-carbohydrate diet protected, despite the high monosaccharide and starch content. Our study results, therefore, suggest that popular high-fat/high-protein weight-loss diets may enhance CDI risk during antibiotic treatment, possibly due to the synergistic effects of a loss of the microorganisms that normally inhibit C. difficile overgrowth and an abundance of amino acids that promote C. difficile overgrowth. In contrast, a high-carbohydrate diet might be protective, despite reports on the recent evolution of enhanced carbohydrate metabolism in C. difficile.