Basic Microbiology
Philip A. Geis in Cosmetic Microbiology, 2020
Fungal cells are eukaryotic, containing membrane-bound intracellular organelles, but also possess cell walls. However, rather than peptidoglycan (bacterial) or cellulose (plants), the fungal cell wall is composed of glucans, mannans, glycoproteins, trehalose, and chitin (a strong and flexible polysaccharide). Single-celled microscopic fungi are referred to as “yeasts” and contain a single nucleus and ovoid morphology. Yeasts are commonly larger than bacteria and lack extracellular fibers like flagella or fimbriae. Multicellular fungal forms are called “molds” comprising long branching filaments called hyphae with many individual cells where the cytoplasm in the hyphae are contiguous with neighboring cells. The hyphae of molds generally form a tangled mass called a mycelium. “Dimorphic” fungi are those that can alternate between yeast and mold forms depending on environmental conditions. For example, Histoplasma capsulatum grows in the environment as a mold but upon infection of the lung grows exclusively as a yeast form (3).
Microbiological Diagnosis of Fungal Infections
Nancy Khardori in Bench to Bedside, 2018
In clinical practice, fungi are classified into three main groups; the yeast and yeast like, the molds, and the dimorphic fungi. Yeasts are unicellular organisms which multiply by budding. The two important pathogenic yeasts include Candida and Cryptococcus. Other less often encountered yeast species are Trichosporon, Geotrichum, Rhodotorula, etc. which can cause infections in immunocompromised hosts. The molds are long filamentous branching organisms which may be septate (e.g., Aspergillus, Fusarium, Scedosporium, etc.) or aseptate/pauciseptate (Mucormycetes). The molds can also be classified into two broad groups, the phaeohyphomycetes and the hyalohyphomycetes, based on color of the fungi. The phaeohyphomycetes are black and hyalohyphomycetes are hyaline. The dimorphic fungi have two morphologies and occur as yeast form in tissue and mold form in the environment. The dimorphic fungi include Histoplasma capsulatum, Blastomyces dermatitidis, Coccidioides immitis, Paracoccidioides brasiliensis, Sporothrix schenckii and Talaromyces marneffei.
Lipids and Dimorphism of Candida Albicans and Sporothrix Schenckii
Rajendra Prasad, Mahmoud A. Ghannoum in Lipids of Pathogenic Fungi, 2017
Phospholipids are the major components of cell membranes. Most membranes contain different classes of phospholipids and their compositions are rather constant in a given membrane under the same growth conditions. Some membrane-bound enzymes require specific lipids and proper physical states, i.e., fluidity of membranes for their optimal activities.12 In addition to these functions, phospholipids play a key role in signal transduction.17 Morphological interconversion between the yeast and mycelial forms of dimorphic fungus depends on the growth conditions, and their changes are related to intracellular signal transduction. Therefore, analysis of the membrane phospholipid composition of the yeast and mycelial cells should shed light on the mechanism of dimorphism and virulence.
The expanding use of matrix-assisted laser desorption/ionization-time of flight mass spectroscopy in the diagnosis of patients with mycotic diseases
Published in Expert Review of Molecular Diagnostics, 2019
Thomas J. Walsh, Matthew W. McCarthy
Thus far, we have considered the role of MALDI-TOF MS in the identification of yeasts and molds. However, some organisms display characteristics of both yeasts and molds, depending on the temperature. Dimorphic fungi are fungi that can reproduce as either a mold or a yeast-like state [56]. Many of these organisms, which include species of Histoplasma, Blastomyces, Coccidioides, Paracoccidioides, Talaromyces, and Sporothrix, demonstrate the mold form at 25°C and the yeast at 37°C [57]. Proper identification requires a high index of suspicion, as the isolation of the pathogenic fungus from cultures together with the visualization of typical organisms in tissues are the gold standard methods for diagnosis. However, cultures are time-consuming, and some require level 3 containment and often require experienced personnel.
Tailoring and optimization of a honey-based nanoemulgel loaded with an itraconazole–thyme oil nanoemulsion for oral candidiasis
Published in Drug Delivery, 2023
Amal M. Sindi, Waleed Y. Rizg, Muhammad Khalid Khan, Hala M. Alkhalidi, Waleed S. Alharbi, Fahad Y. Sabei, Eman Alfayez, Hanaa Alkharobi, Mohammed Korayem, Mohammed Majrashi, Majed Alharbi, Mohammed Alissa, Awaji Y. Safhi, Abdulmajeed M. Jali, Khaled M. Hosny
Free-living eukaryotic organisms known as fungi can be molds (filamentous fungi), yeasts (round fungi), or a blend of both (dimorphic fungi) (Terezhalmy & Huber, 2011). One of the common fungal infections of the oral mucus membranes is oral candidiasis (Prasanna, 2012). It is caused by the yeast Candida albicans, which is a fairly normal component of the oral microbiota; it is found in 30% to 50% of people. As people age, the rate of carriage rises (Dangi et al., 2010). In 60% of patients over 60 years of age with dental problems, C. albicans is recovered from their mouths (Parihar, 2011). In addition to C. albicans, there are several other species of Candida that can be found in the oral environment, including Candida guilliermondii, Candida krusei, Candida glabrata, Candida parapsilosis, Candida pseudotropicalis, and Candida tropicalis (Dangi et al., 2010).
Disseminated histoplasmosis: case report and review of the literature
Published in Acta Clinica Belgica, 2018
Séverine Evrard, Philippe Caprasse, Pierre Gavage, Myriam Vasbien, Jean Radermacher, Marie-Pierre Hayette, Rosalie Sacheli, Marjan Van Esbroeck, Lieselotte Cnops, Eric Firre, Laurent Médart, Filip Moerman, Jean-Marc Minon
Histoplasma capsulatum var. capsulatum is a dimorphic fungus. Its saprobic mold form grows in soils contaminated by bird and bat droppings. People are infected by inhaling microconidia, particularly in confined spaces such as caves, farms, silos, dovecotes, or chicken-farms. There is no interhuman transmission. Disease occurs worldwide and is highly prevalent in areas along the Mississippi and Ohio valleys of the USA and in Central and South Africa [5]. Europe only has a few endemic locations in a part of Italy (Emilia-Romagna area) [4] and in Germany, where the fungus has been found in the soil [6]. Most of the cases encountered in Europe are imported through immigration, from people often co-infected with HIV [5]. Disseminated histoplasmosis is a criterion for AIDS definition since 1987.
Related Knowledge Centers
- Blastomyces Dermatitidis
- Blastomycosis
- Candida Albicans
- Coccidioides Immitis
- Histoplasma Capsulatum
- Thermoregulation
- Yeast
- Talaromyces Marneffei
- Paracoccidioides Brasiliensis
- Sporotrichosis