Candida albicans is an opportunistic pathogenic yeast that is a common member of the human gut flora. It can also survive outside the human body. It is detected in the gastrointestinal tract and mouth in 40–60% of healthy adults. It is usually a commensal organism, but it can become pathogenic in immunocompromised individuals under a variety of conditions. It is one of the few species of the genus Candida that cause the human infection candidiasis, which results from an overgrowth of the fungus. Candidiasis is, for example, often observed in HIV-infected patients. C. albicans is the most common fungal species isolated from biofilms either formed on (permanent) implanted medical devices or on human tissue. C. albicans, C. tropicalis, C. parapsilosis, and C. glabrata are together responsible for 50–90% of all cases of candidiasis in humans. A mortality rate of 40% has been reported for patients with systemic candidiasis due to C. albicans. By one estimate, invasive candidiasis contracted in a hospital causes 2,800 to 11,200 deaths yearly in the US. Nevertheless, these numbers may not truly reflect the true extent of damage this organism causes, given new studies indicating that C. albicans can cross the blood–brain barrier in mice.
Cryptococcus neoformans is an encapsulated yeast belonging to the class Tremellomycetes and an obligate aerobe that can live in both plants and animals. Its teleomorph is a filamentous fungus, formerly referred to Filobasidiella neoformans. In its yeast state, it is often found in bird excrement. Cryptococcus neoformans can cause disease in apparently immunocompetent, as well as immunocompromised, hosts.
Aspergillus fumigatus is a species of fungus in the genus Aspergillus, and is one of the most common Aspergillus species to cause disease in individuals with an immunodeficiency.
Aspergillus is a genus consisting of several hundred mold species found in various climates worldwide.
Fungal infection, also known as mycosis, is a disease caused by fungi. Different types are traditionally divided according to the part of the body affected; superficial, subcutaneous, and systemic. Superficial fungal infections include common tinea of the skin, such as tinea of the body, groin, hands, feet and beard, and yeast infections such as pityriasis versicolor. Subcutaneous types include eumycetoma and chromoblastomycosis, which generally affect tissues in and beneath the skin. Systemic fungal infections are more serious and include cryptococcosis, histoplasmosis, pneumocystis pneumonia, aspergillosis and mucormycosis. Signs and symptoms range widely. There is usually a rash with superficial infection. Fungal infection within the skin or under the skin may present with a lump and skin changes. Pneumonia-like symptoms or meningitis may occur with a deeper or systemic infection.
An opportunistic infection is an infection caused by pathogens that take advantage of an opportunity not normally available. These opportunities can stem from a variety of sources, such as a weakened immune system, an altered microbiome, or breached integumentary barriers. Many of these pathogens do not necessarily cause disease in a healthy host that has a non-compromised immune system, and can, in some cases, act as commensals until the balance of the immune system is disrupted. Opportunistic infections can also be attributed to pathogens which cause mild illness in healthy individuals but lead to more serious illness when given the opportunity to take advantage of an immunocompromised host.
Aspergillosis is a fungal infection of usually the lungs, caused by the genus Aspergillus, a common mould that is breathed in frequently from the air, but does not usually affect most people. It generally occurs in people with lung diseases such as asthma, cystic fibrosis or tuberculosis, or those who are immunocompromised such as those who have had a stem cell or organ transplant or those who take medications such as steroids and some cancer treatments which suppress the immune system. Rarely, it can affect skin.
Gliotoxin is a sulfur-containing mycotoxin that belongs to a class of naturally occurring 2,5-diketopiperazines produced by several species of fungi, especially those of marine origin. It is the most prominent member of the epipolythiopiperazines, a large class of natural products featuring a diketopiperazine with di- or polysulfide linkage. These highly bioactive compounds have been the subject of numerous studies aimed at new therapeutics. Gliotoxin was originally isolated from Gliocladium fimbriatum, and was named accordingly. It is an epipolythiodioxopiperazine metabolite that is one of the most abundantly produced metabolites in human invasive Aspergillosis (IA).
Echinocandins are a class of antifungal drugs that inhibit the synthesis of β-glucan in the fungal cell wall via noncompetitive inhibition of the enzyme 1,3-β glucan synthase. The class has been dubbed the "penicillin of antifungals," along with the related papulacandins, as their mechanism of action resembles that of penicillin in bacteria. β-glucans are carbohydrate polymers that are cross-linked with other fungal cell wall components, the fungal equivalent to bacterial peptidoglycan. Caspofungin, micafungin, and anidulafungin are semisynthetic echinocandin derivatives with limited clinical use due to their solubility, antifungal spectrum, and pharmacokinetic properties.
Aspergillus terreus, also known as Aspergillus terrestris, is a fungus (mold) found worldwide in soil. Although thought to be strictly asexual until recently, A. terreus is now known to be capable of sexual reproduction. This saprotrophic fungus is prevalent in warmer climates such as tropical and subtropical regions. Aside from being located in soil, A. terreus has also been found in habitats such as decomposing vegetation and dust. A. terreus is commonly used in industry to produce important organic acids, such as itaconic acid and cis-aconitic acid, as well as enzymes, like xylanase. It was also the initial source for the drug mevinolin (lovastatin), a drug for lowering serum cholesterol.
A dimorphic fungus is a fungus that can exist in the form of both mold and yeast. As this is usually brought about by a change in temperature, this fungus type is also described as a thermally dimorphic fungus. An example is Talaromyces marneffei, a human pathogen that grows as a mold at room temperature, and as a yeast at human body temperature.
A blastoconidium is an asexual holoblastic conidia formed through the blowing out or budding process of a yeast cell, which is a type of asexual reproduction that results in a bud arising from a parent cell. The production of a blastoconidium can occur along a true hyphae, pseudohyphae, or a singular yeast cell. The word "conidia" comes from the Greek word konis and eidos, konis meaning dust and eidos meaning like. The term "bud" comes from the Greek word blastos, which means bud. Yeasts such as Candida albicans and Cryptococcus neoformans produce these budded cells known as blastoconidia.
Fungal meningitis refers to meningitis caused by a fungal infection.
In biology, a pathogen, in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ.
Mycobiota are a group of all the fungi present in a particular geographic region or habitat type. An analogous term for Mycobiota is funga.
Vomocytosis is the cellular process by phagocytes expel live organisms that they have engulfed without destroying the organism. Vomocytosis is one of many methods used by cells to expel internal materials into their external environment, yet it is distinct in that both the engulfed organism and host cell remain undamaged by expulsion. As engulfed organisms are released without being destroyed, vomocytosis has been hypothesized to be utilized by pathogens as an escape mechanism from the immune system. The exact mechanisms, as well as the repertoire of cells that utilize this mechanism, are currently unknown, yet interest in this unique cellular process is driving continued research with the hopes of elucidating these unknowns.
Arturo Casadevall is a Bloomberg Distinguished Professor of Molecular Microbiology & Immunology and Infectious Diseases at the Johns Hopkins Bloomberg School of Public Health and Johns Hopkins School of Medicine, and the Alfred and Jill Sommer Professor and Chair of the W. Harry Feinstone Department of Molecular Microbiology and Immunology at the Johns Hopkins Bloomberg School of Public Health. He is an internationally recognized expert in infectious disease research, with a focus on fungal and bacterial pathogenesis and basic immunology of antibody structure-function. He was elected a member of the National Academy of Sciences in 2022.
Edouard Drouhet was a physician, biologist, and medical mycologist who played a key role in understanding how anti-fungal agents such as ketoconazole and amphotericin-B can be used as therapeutic treatments in humans with superficial or deep-seated mycoses.
Dectin-2 or C-type lectin domain containing 6A is a protein that in humans is encoded by the CLEC6A gene. Dectin-2 is a member of the C-type lectin/C-type lectin-like domain (CTL/CTLD) superfamily. The encoded protein is a type II transmembrane protein with an extracellular carbohydrate recognition domain. It functions as a pattern recognition receptor recognizing α-mannans and as such plays an important role in innate immune response to fungi. Expression is found on macrophages and dendritic cells. It can also be found at low levels in Langerhans cells and peripheral blood monocytes, where expression levels could be increased upon induction of inflammation.
