Intestinal bacteria-a powerful weapon for fungal infections treatment

The morbidity and mortality of invasive fungal infections are rising gradually. In recent years, fungi have quietly evolved stronger defense capabilities and increased resistance to antibiotics, posing huge challenges to maintaining physical health. Therefore, developing new drugs and strategies to combat these invasive fungi is crucial. There are a large number of microorganisms in the intestinal tract of mammals, collectively referred to as intestinal microbiota. At the same time, these native microorganisms co-evolve with their hosts in symbiotic relationship. Recent researches have shown that some probiotics and intestinal symbiotic bacteria can inhibit the invasion and colonization of fungi. In this paper, we review the mechanism of some intestinal bacteria affecting the growth and invasion of fungi by targeting the virulence factors, quorum sensing system, secreting active metabolites or regulating the host anti-fungal immune response, so as to provide new strategies for resisting invasive fungal infection.

Candida albicans in celiac disease: A wolf in sheep's clothing

Candida albicans is a commensal fungus with a potential pathogenicity and celiac disease is an autoimmune condition. Both share multiple pathophysiological junctions, including serological markers against cell-wall proteins of Candida, anti-gliadin antibodies are positive in both entities, gluten and a candidal virulence factor share sequence similarity and the autoantigen of celiac disease, the tissue transglutaminase, is pivotal in Candida albicans commensalism and hostile behavior and its covalently cross linked products are stable and resistant to breakdown in the two entities. Those autoimmune/infectious cross roads are the basis for the hypothesis that Candida albicans is an additional environmental factor for celiac disease autoimmunogenesis.

The Biological Fight Against Pathogenic Bacteria and Protozoa

The animal gastrointestinal tract is a tube with two open ends; hence, from the microbial point of view it constitutes an open system, as opposed to the circulatory system that must be a tightly closed microbial-free environment. In particular, the human intestine spans ca. 200 m² and represents a massive absorptive surface composed of a layer of epithelial cells as well as a paracellular barrier. The permeability of this paracellular barrier is regulated by transmembrane proteins known as claudins that play a critical role in tight junctions.

Systems Level Dissection of Candida Recognition by Dectins: A Matter of Fungal Morphology and Site of Infection

Candida albicans is an ubiquitous fungal commensal of human skin and mucosal surfaces, and at the same time a major life-threatening human fungal pathogen in immunocompromised individuals. Host defense mechanisms rely on the capacity of professional phagocytes to recognize Candida cell wall antigens. During the past decade, the host immune response to Candida was dissected in depth, highlighting the essential role of C-type lectin receptors, especially regarding the power of the Dectins’ family in discriminating between the tolerated yeast-like form of Candida and its invading counterpart, the hyphae. This review focuses on the immuno-modulatory properties of the Candida morphologies and their specific interactions with the host innate immune system in different body surfaces.

Mycobiota in gastrointestinal diseases

New insights gained through the use of state-of-the-art technologies, including next-generation sequencing, are starting to reveal that the association between the gastrointestinal tract and the resident mycobiota (fungal community) is complex and multifaceted, in which fungi are active participants influencing health and disease. Characterizing the human mycobiome (the fungi and their genome) in healthy individuals showed that the gastrointestinal tract contains 66 fungal genera and 184 fungal species, with Candida as the dominant fungal genera. Although fungi have been associated with a number of gastrointestinal diseases, characterization of the mycobiome has mainly been focused on patients with IBD and graft-versus-host disease. In this Review, we summarize the findings from studies investigating the relationship between the gut mycobiota and gastrointestinal diseases, which indicate that fungi contribute to the aggravation of the inflammatory response, leading to increased disease severity. A model explaining the mechanisms underlying the role of the mycobiota in gastrointestinal diseases is also presented. Our understanding of the contribution of the mycobiota to health and disease is still in its infancy and leaves a number of questions to be addressed. Answering these questions might lead to novel approaches to prevent and/or manage acute as well as chronic gastrointestinal disease.

Candida albicans morphogenesis and host defence: discriminating invasion from colonization

Candida albicans is a common fungal pathogen of humans that colonizes the skin and mucosal surfaces of most healthy individuals. Until recently, little was known about the mechanisms by which mucosal antifungal defences tolerate colonizing C. albicans but react strongly when hyphae of the same microorganism attempt to invade tissue. In this Review, we describe the properties of yeast cells and hyphae that are relevant to their interaction with the host, and the immunological mechanisms that differentially recognize colonizing versus invading C. albicans.

New nonculture-based methods for the diagnosis of invasive candidiasis

PURPOSE OF REVIEW

Invasive candidiasis is a severe infectious complication occurring mostly in onco-hematologic and surgical patients. Its conventional diagnosis is insensitive and often late, leading to a delayed treatment and a high mortality. The purpose of this article is to review recent contributions in the nonconventional diagnostic approaches of invasive candidiasis, both for the detection of the epidose and the characterization of the etiologic agent.

RECENT FINDINGS

Antigen-based tests to detect invasive candidiasis comprise a specific test, mannan, as well as a nonspecific test, beta-D-glucan. Both have a moderate sensitivity and a high specificity, and cannot be recommended alone as a negative screening tool or a positive syndrome driven diagnostic tool. Molecular-based tests still have not reached the stage of rapid, easy to use, standardized tests ideally complementing blood culture at the time of blood sampling. New tests (fluorescence in-situ hybridization or mass spectrometry) significantly reduce the delay of identification of Candida at the species level in positive blood cultures, and should have a positive impact on earlier appropriate antifungal therapy and possibly on outcome.

SUMMARY

Both antigen-based and molecular tests appear as promising new tools to complement and accelerate the conventional diagnosis of invasive candidiasis with an expected significant impact on earlier and more focused treatment and on prognosis.

Autism spectrum disorders and allergy: observation from a pediatric allergy/immunology clinic

IgE-mediated allergic diseases (e.g., allergic rhinoconjunctivitis, atopic asthma and food allergy) are prevalent (up to 30%) in the general population and are increasing in developed countries. In infants and young children, non-IgE-mediated food allergy is also prevalent. In addition to easily recognized organ-specific symptoms, allergic diseases can cause neuropsychiatric symptoms, such as irritability and hyperactivity, in otherwise healthy individuals. This is also likely to occur in children with autism spectrum disorder (ASD). Moreover, the discomfort and pain associated with allergic diseases could aggravate behavioral symptoms in ASD children. Allergic conditions are easily treatable; however, ASD children may be underdiagnosed and/or undertreated for allergic and other common childhood diseases, in part due to their impaired communication skills. Practicing physicians should be aware of the potential impact of allergic diseases on behavioral symptoms and cognitive activity in ASD children. However, they also need to be aware that certain symptoms often attributed to 'allergy' by caregivers may not be immune mediated and should understand that behavioral symptoms can also be affected by many non-IgE-mediated causes.

[Immunopathogenesis of inflammatory bowel disease]

Inflammatory bowel diseases (IBD) are idiopathic, chronic and relapsing inflammatory conditions of the gastrointestinal tract. New insights into the pathogenesis of IBD have been provided by three lines of research: (1) studying susceptibility genes involved in the detection of bacterial components and in the regulation of the host immune response, (2) highlighting the disruption of tolerance towards the commensal microbiota and (3) unravelling the critical role of environmental factors such as sanitation and hygiene. This review presents current etiological hypothesis of IBD which argue that pathogenic intestinal bacteria and/or infectious agents initiate and perpetuate the inflammation of the gut in an individual with genetic vulnerability leading to impaired epithelial barrier function and abnormal mucosal immune responses.

[C. elegans defence mechanisms]

The nematode Caenorhabditis elegans has evolved as a powerful invertebrate model to study innate immunity to pathogens. C. elegans possesses inducible defence mechanisms to protect itself from pathogenic attack, mainly by the production of antimicrobial effector molecules. Its innate immune system is under the control of a surprisingly complex network of evolutionary conserved signalling pathways, which are activated depending on the pathogen, suggesting that C. elegans is able to mount a specific defence response to different pathogens. In this review we will introduce the worm's immune system and discuss the different signalling pathways that regulate its response to bacterial pathogens which mainly infect C. elegans by an oral route and by invading its intestine, before focusing our attention on the resistance of C. elegans to a natural occurring fungal -pathogen that infects the worm by invading its -epidermis.