Acinetobacter junii: an emerging One Health pathogen.

Acinetobacter junii is an opportunistic human and animal pathogen severely understudied. Here, we conducted the largest genomic epidemiological study on this pathogen to date. Our data show that this bacterium has spread globally. Also, we found that some human and non-human isolates are not well differentiated from one another, implying transmission between clinical and non-clinical, non-human settings. Remarkably, human but also some non-human isolates have clinically important antibiotic resistance genes, and some of these genes are located in plasmids. Given these results, we put forward that A. junii should be considered an emerging One Health problem. In this regard, future molecular epidemiological studies about this species will go beyond human isolates and will consider animal-, plant-, and water-associated environments. IMPORTANCE: Acinetobacter baumannii is the most well-known species from the genus Acinetobacter. However, other much less studied Acinetobacter species could be important opportunistic pathogens of animals, plants and humans. Here, we conducted the largest genomic epidemiological study of A. junii, which has been described as a source not only of human but also of animal infections. Our analyses show that this bacterium has spread globally and that, in some instances, human and non-human isolates are not well differentiated. Remarkably, some non-human isolates have important antibiotic resistance genes against important antibiotics used in human medicine. Based on our results, we propose that this pathogen must be considered an issue not only for humans but also for veterinary medicine.

Oral pathobiont Klebsiella chaperon usher pili provide site-specific adaptation for the inflamed gut mucosa.

The ectopic gut colonization by orally derived pathobionts has been implicated in the pathogenesis of various gastrointestinal diseases, including inflammatory bowel disease (IBD). For example, gut colonization by orally derived Klebsiella spp. has been linked to IBD in mice and humans. However, the mechanisms whereby oral pathobionts colonize extra-oral niches, such as the gut mucosa, remain largely unknown. Here, we performed a high-density transposon (Tn) screening to identify genes required for the adaptation of an oral Klebsiella strain to different mucosal sites - the oral and gut mucosae - at the steady state and during inflammation. We find that K. aerogenes, an oral pathobiont associated with both oral and gut inflammation in mice, harbors a newly identified genomic locus named "locus of colonization in the inflamed gut (LIG)" that encodes genes related to iron acquisition (Sit and Chu) and host adhesion (chaperon usher pili [CUP] system). The LIG locus is highly conserved among K. aerogenes strains, and these genes are also present in several other Klebsiella species. The Tn screening revealed that the LIG locus is required for the adaptation of K. aerogenes in its ectopic niche. In particular, we determined K. aerogenes employs a CUP system (CUP1) present in the LIG locus for colonization in the inflamed gut, but not in the oral mucosa. Thus, oral pathobionts likely exploit distinct adaptation mechanisms in their ectopically colonized intestinal niche compared to their native niche.

Microbiota-dependent activation of CD4+ T cells induces CTLA-4 blockade-associated colitis via Fcγ receptors.

Immune checkpoint inhibitors can stimulate antitumor immunity but can also induce toxicities termed immune-related adverse events (irAEs). Colitis is a common and severe irAE that can lead to treatment discontinuation. Mechanistic understanding of gut irAEs has been hampered because robust colitis is not observed in laboratory mice treated with checkpoint inhibitors. We report here that this limitation can be overcome by using mice harboring the microbiota of wild-caught mice, which develop overt colitis following treatment with anti-CTLA-4 antibodies. Intestinal inflammation is driven by unrestrained activation of IFNγ-producing CD4+ T cells and depletion of peripherally induced regulatory T cells through Fcγ receptor signaling. Accordingly, anti-CTLA-4 nanobodies that lack an Fc domain can promote antitumor responses without triggering colitis. This work suggests a strategy for mitigating gut irAEs while preserving antitumor stimulating effects of CTLA-4 blockade.

Photocatalytic activity of silver nanoparticles@cellulose nanocomposites, from pistachio husk, in the toxic azo commercial dye degradation.

In this work, an over-the-counter commercial dye, containing direct blue 151 in its composition, which is also discarded without any environmental regulation, was efficiency photodegraded using a green chemistry-synthesized nanocomposites type silver nanoparticles (AgNPs) supported on pistachio husk (PH). The green synthesis (GS) of the nanocomposites was carried out using the Anemopsis californica leaf extract (ExAc) as a reducing-stabilizing agent (AgNPs/ExAc-PH), for the first time. The presence of AgNPs on the nanocomposite surface was corroborated by field emission transmission electron microscope (FE-TEM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The synthesized AgNPs/ExAc-PH has a bimodal size of 24 and 25 nm (4.86 % each) and a 0.72 % of AgNPs on its surface. AgNPs were adhered to the PH surface, through secondary bonds between the Ag and the cellulose of the PH. The optimum conditions, for efficient photocatalytic degradation, were 5 mg of nanocomposite, 3.18 × 10-2 M of NaBH4, natural sunlight, and stirring; this results in a photodegradation efficiency of 100 % almost instantaneously. Furthermore, it was shown that the dye degradation process is primarily due to the photocatalytic degradation of the dye, which occurs almost instantaneously.

Fiber-deficient diet inhibits colitis through the regulation of the niche and metabolism of a gut pathobiont.

Exclusive enteral nutrition (EEN) with fiber-free diets is an effective steroid-sparing treatment to induce clinical remission in children with Crohn's disease (CD). However, the mechanism underlying the beneficial effects of EEN remains obscure. Using a model of microbiota-dependent colitis with the hallmarks of CD, we find that the administration of a fiber-free diet prevents the development of colitis and inhibits intestinal inflammation in colitic animals. Remarkably, fiber-free diet alters the intestinal localization of Mucispirillum schaedleri, a mucus-dwelling pathobiont, which is required for triggering disease. Mechanistically, the absence of dietary fiber reduces nutrient availability and impairs the dissimilatory nitrate reduction to ammonia (DNRA) metabolic pathway of Mucispirillum, leading to its exclusion from the mucus layer and disease remission. Thus, appropriate localization of the specific pathobiont in the mucus layer is critical for disease development, which is disrupted by fiber exclusion. These results suggest strategies to treat CD by targeting the intestinal niche and metabolism of disease-causing microbes.

Phenolics from Chilean Bee Bread Exhibit Antioxidant and Antibacterial Properties: The First Prospective Study.

Bee bread (BB) is a beehive product generated upon fermentation of pollen combined with flower nectar and glandular secretions. The potential application of BB is related to its nutritional and functional components, including phenolic compounds. This is the first prospective study on palynological parameters, phenolics, antioxidant, and antibacterial activity of Chilean bee bread in vitro. The tested material exhibited high levels of phenolics (1340±186 mg GAE/100 g BB) and showed antioxidant capacity as determined by the FRAP (51±2 µmol Trolox equivalent/g BB) and ORAC-FL (643±64 µmol Trolox equivalent/g BB) and antibacterial activity against Streptococcus pyogenes. Furthermore, the phenolic acids and flavonoids was determined using liquid chromatography-mass spectrometry, and the concentration was determined using liquid chromatography with diode array detection. Kaempferol, quercetin, ferulic acid, and rutin were the main phenolics found. This study demonstrates the bioactive potential of Chilean BB and supports the evidence that this bee product is a promising source of antioxidants and antimicrobial compounds.

Pseudomonas aeruginosa hijacks the murine nitric oxide metabolic pathway to evade killing by neutrophils in the lung.

Neutrophils play a critical role in the eradication of Pseudomonas aeruginosa, a major pathogen causing lung infection. However, the mechanisms used by the pathogen to evade neutrophil-mediated killing remain poorly understood. Using a high-density transposon screen, we find that P. aeruginosa colonization in the lung is promoted by pathogen nitrite reductase nirD. nirD is required for ammonia production from nitrite, a metabolite derived from nitrogen oxide (NO) generated by inducible NO synthetase (iNOS) in phagocytes. P. aeruginosa deficient in nirD exhibit reduced survival in wild-type neutrophils but not in iNOS-deficient neutrophils. Mechanistically, nirD enhances P. aeruginosa survival in neutrophils by inhibiting the localization of the pathogen in late phagosomes. P. aeruginosa deficient in nirD show impaired lung colonization after infection in wild-type mice but not in mice with selective iNos deficiency in neutrophils. Thus, P. aeruginosa uses neutrophil iNOS-mediated NO production to limit neutrophil pathogen killing and to promote its colonization in the lung.

Photocatalytic Activity and Biocide Properties of Ag-TiO2 Composites on Cotton Fabrics.

Composites of Ag and TiO2 nanoparticles were synthesized in situ on cotton fabrics using sonochemical and solvothermal methods achieving the successive formation of Ag-NPs and Ti-NPs directly on the fabric. The impregnated fabrics were characterized using ATR-FTIR spectroscopy; high-resolution microscopy (HREM); scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDS); Raman, photoluminescence, UV-Vis, and DRS spectroscopies; and by tensile tension tests. Results showed the successful formation and impregnation of NPs on the cotton fabric, with negligible leaching of NPs after several washing cycles. The photocatalytic activity of supported NPs was assessed by the degradation of methyl blue dye (MB) under solar and UV irradiation revealing improved photocatalytic activity of the Ag-TiO2/cotton composites due to a synergy of both Ag and TiO2 nanoparticles. This behavior is attributed to a diminished electron-hole recombination effect in the Ag-TiO2/cotton samples. The biocide activity of these composites on the growth inhibition of Staphylococcus aureus (Gram+) and Escherichia coli (Gram-) was confirmed, revealing interesting possibilities for the utilization of the functionalized cotton fabric as protective cloth for medical applications.

Evaluación de la calidad de los huevos / Evaluation of eggs quality

Introducción: En el ámbito de las enfermedades transmitidas por alimentos, la Salmonella spp. puede causar salmonelosis, principalmente, a través del huevo de gallina, integrante alimentario básico, del cual se pueden evaluar diversos parámetros cualitativos. El objetivo del estudio fue evaluar la calidad y la presencia de Salmonella spp. en huevos expendidos en Libertador San Martín, Entre Ríos. Material y métodos: El estudio fue desarrollado en el Laboratorio de Nutrición de la Universidad Adventista del Plata en Libertador San Martín, y un Laboratorio de análisis químicos en Paraná, desde mayo hasta agosto de 2020. El diseño fue descriptivo, retrospectivo y de corte transversal. La muestra estuvo constituida por 114 huevos obtenidos de 3 supermercados locales, en los cuales se encuentran representados todos los proveedores de huevos de la ciudad. Resultados: No se aisló Salmonella spp. En ninguna de las muestras analizadas. Cada unidad estuvo limpia, aunque 49 no presentaron yema céntrica, siendo el 57,01 % (n = 65) de calidad A, respecto de la cáscara y contenido. El peso promedio fue de 56,89 g, predominando los huevos grandes, DE ± 3,72. Para el Índice de forma la media fue 74,71, DE ± 2,45, destacándose los de forma óptima. Con referencia a la prueba de flotación, la mayoría fueron frescos del día. Respecto del Índice de yema, la media fue 0,38, DE ± 0,09, clasificándose la mayoría debajo de calidad B. Hubo una relación estadísticamente significativa entre este último parámetro y el estado de la cáscara y contenido (p = 0,010). El pH promedio de la clara fue 8,8, DE ± 0,39 y de la yema 8,0, DE ± 0,71. Conclusiones: Los parámetros cualitativos y el microbiológico son aceptables, excepto el Índice y pH de yema. Es imprescindible seguir procurando la inocuidad del huevo

Introduction: In the field of foodborne diseases, Salmonella spp. can cause salmonellosis through foods such as chicken eggs, a basic food component, of which various qualitative parameters can be evaluated. The objective of the study was to evaluate the quality and the presence of Salmonella spp. in eggs sold in Libertador San Martín, Entre Ríos. Material and methods: The study was developed in the Nutrition Laboratory of the Universidad Adventista del Plata in Libertador San Martín, and a Chemical Analysis Laboratory in Paraná, from May to August 2020. The design was descriptive, retrospective and cross-sectional. The sample consisted of 114 eggs obtained from 3 local supermarkets, in which all egg suppliers in the city were represented. Results: Salmonella spp. wasn´t isolated in none of the samples analyzed. Each unit was clean, although 49 did not present centric yolk, being 57.01 % (n = 65) of A quality, with respect to the shell and content. The average weight was 56.89 g, with a predominance of large eggs, SD ± 3.72. For the shape index, the mean was 74.71, SD ± 2.45, highlighting those with optimal shape. With reference to the flotation test, most were fresh from the day. Regarding the yolk index, the mean was 0.38, SD ± 0.09, with the majority classified below B quality. There was a statistically significant relationship between this last parameter and the state of the shell and content (p = 0.010). The average pH of the white was 8.8, SD ± 0.39 and of the yolk 8.0, SD ± 0.71. Conclusions: The qualitative and microbiological parameters are acceptable, except the index and pH of the yolk. It is essential to continue ensuring the safety of the egg

Microbiota-mediated colonization resistance: mechanisms and regulation.

A dense and diverse microbial community inhabits the gut and many epithelial surfaces. Referred to as the microbiota, it co-evolved with the host and is beneficial for many host physiological processes. A major function of these symbiotic microorganisms is protection against pathogen colonization and overgrowth of indigenous pathobionts. Dysbiosis of the normal microbial community increases the risk of pathogen infection and overgrowth of harmful pathobionts. The protective mechanisms conferred by the microbiota are complex and include competitive microbial-microbial interactions and induction of host immune responses. Pathogens, in turn, have evolved multiple strategies to subvert colonization resistance conferred by the microbiota. Understanding the mechanisms by which microbial symbionts limit pathogen colonization should guide the development of new therapeutic approaches to prevent or treat disease.

The NLRP3 inflammasome: activation and regulation.

The NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3) inflammasome is a cytoplasmic supramolecular complex that is activated in response to cellular perturbations triggered by infection and sterile injury. Assembly of the NLRP3 inflammasome leads to activation of caspase-1, which induces the maturation and release of interleukin-1ß (IL-1ß) and IL-18, as well as cleavage of gasdermin D (GSDMD), which promotes a lytic form of cell death. Production of IL-1ß via NLRP3 can contribute to the pathogenesis of inflammatory disease, whereas aberrant IL-1ß secretion through inherited NLRP3 mutations causes autoinflammatory disorders. In this review, we discuss recent developments in the structure of the NLRP3 inflammasome, and the cellular processes and signaling events controlling its assembly and activation.

Characterization and photocatalytic activity of TiO2 nanoparticles on cotton fabrics, for antibacterial masks.

The in-situ impregnation of two commercial cotton fabrics (lab coat and Indiolino) with TiO2 nanoparticles (TiO2-NPs) was carried out. For this, two commercial cotton fabrics were dipped in titanium isopropoxide, titanium butoxide and titanium tetrachloride solutions to the TiO2-NPs formation and in-situ TiO2-NPs impregnation on the cotton fabric surface by the sonochemical, hydrothermal and solvothermal methods, respectively. The impregnated fabrics were characterized by ATR-FTIR, SEM-EDS, Raman, UV-Vis, DRS and tension tests. The results showed the successful formation and impregnation of TiO2-NPs on both cotton fabrics. The leaching of TiO2-NPs from cotton fabrics was negligible after several washing cycles. The self-cleaning properties and antibacterial activity of TiO2-NPs functionalized cotton fabrics were assessed by photocatalytic and antibacterial tests. The photocatalytic activity was determined by the degradation of methylene blue dye under UV and solar irradiation. The materials showed good photoactivity, since MB was degraded up to 99% under solar and UV irradiations in 60 min. The bactericidal capacity of the TiO2-NPs on fabrics, evaluated in-situ by SEM, showed that Indiolino presented the best antibacterial properties against Escherichia coli and Bacillus pumilus.

Purpura fulminans due to Vibrio vulnificus severe infection.

Purpura fulminans is a life-threatening disease, characterized by disseminated intravascular coagulation and endovascular thrombosis; can often occur secondary to heterogeneous etiologies, such as sepsis, and to a lesser extent, secondary to sepsis due to halophilic bacteria, such as V. vulnificus, found in marine environments. Patients with specific comorbidities are at the highest risk of worst scenarios, without prompt treatment, infection can rapidly evolve to fatal, with a mortality rate close to 100 %. We present a case of Purpura fulminans due to V. vulnificus septicemia.

Cooperative action of gut-microbiota-accessible carbohydrates improves host metabolic function.

Microbiota-accessible carbohydrates (MACs) exert health-promoting effects, but how each MAC impacts gut microbiota and regulates host physiology remains unclear. Here, we show that l-arabinose and sucrose cooperatively act on gut microbiota and exert anti-obesogenic effects. Specifically, l-arabinose, a monosaccharide that is poorly absorbed in the gut and inhibits intestinal sucrase, suppresses diet-induced obesity in mice in the presence of sucrose. Additionally, the suppressive effect of l-arabinose on adiposity is abrogated in mice lacking the short-chain fatty acid (SCFA) receptors GPR43 and GPR41. Mechanistically, l-arabinose increases the relative abundance of acetate and propionate producers (e.g., Bacteroides), while sucrose enhances SCFA production. Furthermore, l-arabinose and sucrose activate the glycolytic and pentose phosphate pathways of Bacteroides, respectively, indicating that they synergistically promote acetate production through distinct pathways. These findings suggest that each MAC has a unique property and thus may serve as a precision gut-microbiota modulator to promote host homeostasis.

Maternal gut microbiome-induced IgG regulates neonatal gut microbiome and immunity.

The gut microbiome elicits antigen-specific immunoglobulin G (IgG) at steady state that cross-reacts to pathogens to confer protection against systemic infection. The role of gut microbiome-specific IgG antibodies in the development of the gut microbiome and immunity against enteric pathogens in early life, however, remains largely undefined. In this study, we show that gut microbiome-induced maternal IgG is transferred to the neonatal intestine through maternal milk via the neonatal Fc receptor and directly inhibits Citrobacter rodentium colonization and attachment to the mucosa. Enhanced neonatal immunity against oral C. rodentium infection was observed after maternal immunization with a gut microbiome-derived IgG antigen, outer membrane protein A, or induction of IgG-inducing gut bacteria. Furthermore, by generating a gene-targeted mouse model with complete IgG deficiency, we demonstrate that IgG knockout neonates are more susceptible to C. rodentium infection and exhibit alterations of the gut microbiome that promote differentiation of interleukin-17A-producing γδ T cells in the intestine, which persist into adulthood and contribute to increased disease severity in a dextran sulfate sodium-induced mouse model of colitis. Together, our studies have defined a critical role for maternal gut microbiome-specific IgG antibodies in promoting immunity against enteric pathogens and shaping the development of the gut microbiome and immune cells in early life.

Epidermal clearance of Candida albicans is mediated by IL-17 but independent of fungal innate immune receptors.

IL-17 plays important roles in host defense against Candida albicans at barrier surfaces and during invasive infection. However, the role of IL-17 in host defense after colonization of the epidermis, a main site of C. albicans infection, remains poorly understood. Using a murine model of epicutaneous candidiasis without skin abrasion, we found that skin inflammation triggered by epidermal C. albicans colonization was self-limiting with fungal clearance completed by day 7 after inoculation in wild-type mice or animals deficient in IL-17A or IL-17F. In contrast, marked neutrophilic inflammation in the epidermis and impaired fungal clearance were observed in mice lacking both IL-17A and IL-17F. Clearance of C. albicans was independent of Dectin-1, Dectin-2, CARD9 (caspase-recruitment domain family, member 9), TLR2 (Toll-like receptor 2) and MyD88 in the epidermal colonization model. We found that group 3 innate lymphoid cells (ILC3s) and γδT cells were the major IL-17 producers in the epicutaneous candidiasis model. Analyses of Rag2-/- mice and Rag2-/-Il2rg-/- mice revealed that production of IL-17A and IL-17F by ILC3s was sufficient for C. albicans clearance. Finally, we found that depletion of neutrophils impaired C. albicans clearance in the epidermal colonization model. Taken together, these findings indicate a critical and redundant function of IL-17A and IL-17F produced by ILC3s in host defense against C. albicans in the epidermis. The results also suggest that epidermal C. albicans clearance is independent of innate immune receptors or that these receptors act redundantly in fungal recognition and clearance.

Dysregulation of Cytosolic c-di-GMP in Edwardsiella piscicida Promotes Cellular Non-Canonical Ferroptosis.

Programmed cell death plays an important role in modulating host immune defense and pathogen infection. Ferroptosis is a type of inflammatory cell death induced by intracellular iron-dependent accumulation of toxic lipid peroxides. Although ferroptosis has been associated with cancer and other sterile diseases, very little is known about the role of ferroptosis in modulating host-pathogen interactions. We show that accumulation of the secondary messenger bis-(3',5')-cyclic dimeric GMP (c-di-GMP) in the pathogenic bacterium Edwardsiella piscicida (E. piscicida) triggers a non-canonical ferroptosis pathway in infected HeLa cells. Moreover, we observed that the dysregulation of c-di-GMP in E. piscicida promotes iron accumulation, mitochondrial dysfunction, and production of reactive oxygen species, all of which that can be blocked by iron chelator. Importantly, unlike classical ferroptosis that is executed via excess lipid peroxidation, no lipid peroxidation was detected in the infected cells. Furthermore, lipoxygenases inhibitors and lipophilic antioxidants are not able to suppress morphological changes and cell death induced by E. piscicida mutant producing excess c-di-GMP, and this c-di-GMP dysregulation attenuates bacterial virulence in vivo. Collectively, our results reveal a novel non-canonical ferroptosis pathway mediated by bacterial c-di-GMP and provide evidence for a role of ferroptosis in the regulation of pathogen infection.

Listeria toxin promotes phosphorylation of the inflammasome adaptor ASC through Lyn and Syk to exacerbate pathogen expansion.

Inflammasome activation exacerbates infectious disease caused by pathogens such as Listeria monocytogenes, Staphylococcus aureus, and severe acute respiratory syndrome coronavirus 2. Although these pathogens activate host inflammasomes to regulate pathogen expansion, the mechanisms by which pathogen toxins contribute to inflammasome activation remain poorly understood. Here we show that activation of inflammasomes by Listeria infection is promoted by amino acid residue T223 of listeriolysin O (LLO) independently of its pore-forming activity. LLO T223 is critical for phosphorylation of the inflammasome adaptor ASC at amino acid residue Y144 through Lyn-Syk signaling, which is essential for ASC oligomerization. Notably, a Listeria mutant expressing LLO T223A is impaired in inducing ASC phosphorylation and inflammasome activation. Furthermore, the virulence of LLO T223A mutant is markedly attenuated in vivo due to impaired ability to activate the inflammasome. Our results reveal a function of a pathogen toxin that exacerbates infection by promoting phosphorylation of ASC.

G-CSF secreted by mutant IDH1 glioma stem cells abolishes myeloid cell immunosuppression and enhances the efficacy of immunotherapy.

Mutant isocitrate-dehydrogenase 1 (mIDH1) synthesizes the oncometabolite 2-hydroxyglutarate (2HG), which elicits epigenetic reprogramming of the glioma cells' transcriptome by inhibiting DNA and histone demethylases. We show that the efficacy of immune-stimulatory gene therapy (TK/Flt3L) is enhanced in mIDH1 gliomas, due to the reprogramming of the myeloid cells' compartment infiltrating the tumor microenvironment (TME). We uncovered that the immature myeloid cells infiltrating the mIDH1 TME are mainly nonsuppressive neutrophils and preneutrophils. Myeloid cell reprogramming was triggered by granulocyte colony-stimulating factor (G-CSF) secreted by mIDH1 glioma stem/progenitor-like cells. Blocking G-CSF in mIDH1 glioma­bearing mice restores the inhibitory potential of the tumor-infiltrating myeloid cells, accelerating tumor progression. We demonstrate that G-CSF reprograms bone marrow granulopoiesis, resulting in noninhibitory myeloid cells within mIDH1 glioma TME and enhancing the efficacy of immune-stimulatory gene therapy.