Helicobacter spp. are prevalent in wild mice and protect from lethal Citrobacter rodentium infection in the absence of adaptive immunity

Transfer of the gut microbiota from wild to laboratory mice alters the host's immune status and enhances resistance to infectious and metabolic diseases, but understanding of which microbes and how they promote host fitness is only emerging. Our analysis of metagenomic sequencing data reveals that Helicobacter spp. are enriched in wild compared with specific-pathogen-free (SPF) and conventionally housed mice, with multiple species commonly co-colonizing their hosts. We create laboratory mice harboring three non-SPF Helicobacter spp. to evaluate their effect on mucosal immunity and colonization resistance to the enteropathogen Citrobacter rodentium. Our experiments reveal that Helicobacter spp. interfere with C. rodentium colonization and attenuate C. rodentium-induced gut inflammation in wild-type (WT) mice, even preventing lethal infection in Rag2-/- SPF mice. Further analyses suggest that Helicobacter spp. interfere with tissue attachment of C. rodentium, putatively by reducing the availability of mucus-derived sugars. These results unveil pivotal protective functions of wild mouse microbiota constituents against intestinal infection.

A network of small RNAs regulates sporulation initiation in Clostridioides difficile

The obligate anaerobic, enteric pathogen Clostridioides difficile persists in the intestinal tract by forming antibiotic-resistant endospores that contribute to relapsing and recurrent infections. Despite the importance of sporulation for C. difficile pathogenesis, environmental cues and molecular mechanisms that regulate sporulation initiation remain ill-defined. Here, by using RIL-seq to globally capture the Hfq-dependent RNA-RNA interactome, we discovered a network of small RNAs that bind to mRNAs encoding sporulation-related genes. We show that two of these small RNAs, SpoX and SpoY, regulate translation of the master regulator of sporulation, Spo0A, in an opposing manner, which ultimately leads to altered sporulation rates. Infection of antibiotic-treated mice with SpoX and SpoY deletion mutants revealed a global effect on gut colonization and intestinal sporulation. Our work uncovers an elaborate RNA-RNA interactome controlling the physiology and virulence of C. difficile and identifies a complex post-transcriptional layer in the regulation of spore formation in this important human pathogen.

The natural product chlorotonil A preserves colonization resistance and prevents relapsing Clostridioides difficile infection

Clostridioides difficile infections (CDIs) remain a healthcare problem due to high rates of relapsing/recurrent CDIs (rCDIs). Breakdown of colonization resistance promoted by broad-spectrum antibiotics and the persistence of spores contribute to rCDI. Here, we demonstrate antimicrobial activity of the natural product class of chlorotonils against C. difficile. In contrast to vancomycin, chlorotonil A (ChA) efficiently inhibits disease and prevents rCDI in mice. Notably, ChA affects the murine and porcine microbiota to a lesser extent than vancomycin, largely preserving microbiota composition and minimally impacting the intestinal metabolome. Correspondingly, ChA treatment does not break colonization resistance against C. difficile and is linked to faster recovery of the microbiota after CDI. Additionally, ChA accumulates in the spore and inhibits outgrowth of C. difficile spores, thus potentially contributing to lower rates of rCDI. We conclude that chlorotonils have unique antimicrobial properties targeting critical steps in the infection cycle of C. difficile.

Intracellular vesicle movement, cAMP and myosin II in Dictyostelium

Dictyostelium amoebae were analyzed before and after rapid addition of 10(-6) M cAMP for cellular motility, dynamic shape changes, and intracellular particle movement. Before cAMP addition, amoebae moved in a persistent anterior fashion and were elongate with F-actin localized predominantly in the anterior pseudopod. Intracellular particles moved rapidly and anteriorly. Within seconds after 10(-6) M cAMP addition, cells stopped translocating, pseudopod formation ceased, intracellular particle movement was depressed, and F-actin was lost from the pseudopod and concomitantly relocalized in the cell cortex. After 10 seconds, expansion zones reappeared but were small and no longer anteriorly localized. Vesicle movement partially rebounded but was no longer anteriorly directed. The myosin II null mutant HS2215 exhibited both depressed cellular translocation and vesicle movement. The addition of cAMP to HS2215 cells did not result in any detectable change in the random, depressed movement of particles. The results with HS2215 suggest that myosin II is essential for (1) rapid cellular translocation, (2) cellular polarity, (3) rapid particle movement, (4) anteriorly directed particle movement, and (5) the cAMP response. Electron micrographs suggest that at least half of the particles examined in this study contain in turn smaller membrane bound vesicles or multilamellar membrane bodies. The possible role of these vesicles is discussed.

Changes in dental development in paediatric patients with chronic kidney disease

Dental examination of 73 paediatric patients with nephrotic syndrome and 49 with chronic renal failure revealed enamel changes of permanent teeth in about 50%. They consisted usually of white discolorations and hypoplasia of enamel. In nephrotic patients they were observed particularly after the administration of high doses of corticosteroids. In patients with renal failure enamel changes occur very early. Their location was usually compatible with an insult on enamelisation at the time of manifestation of kidney disease. The prevalence of caries was almost twice as high in patients with nephrotic syndrome than in those with renal failure.