Sporothrix brasiliensis | |
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Scientific classification ![]() | |
Domain: | Eukaryota |
Kingdom: | Fungi |
Division: | Ascomycota |
Class: | Sordariomycetes |
Order: | Ophiostomatales |
Family: | Ophiostomataceae |
Genus: | Sporothrix |
Species: | S. brasiliensis |
Binomial name | |
Sporothrix brasiliensis Marimon, Gené, Cano & Guarro (2007) | |
Sporothrix brasiliensis is a fungus that is commonly found in soil. It is an emerging fungal pathogen that is causing disease in humans and cats mainly in Brazil and other countries in South America.
Similar to other species in Sporothrix genus, this fungus causes the disease sporotrichosis. However, it has been observed that more severe disease results from infection by Sporothrix brasiliensis compared to other species. [1] The fungus is a thermally dimorphic fungus as it is found in the mycelium phase at room temperature and as yeast in the warmer temperatures of host bodies. [2]
The two morphologies displayed by Sporothrix brasiliensis are a hyphal form which occurs in the environment and a yeast form which occurs at higher temperatures (36 - 37 °C) such as within the bodies of mammals.
The hyphal form of S.brasiliensis occurs at room temperature. Melaninization level of the hyphal form can vary from light (albino) to dark (pigmented) phenotypes. Sympodial conidia are obovoid shaped with a glassy (hyaline) appearance while sessile conidia are dark colored and globose. [3]
The yeast form of S.brasiliensis occurs at higher temperatures. Micro-morphologically the yeast takes the shape of an elongated cigar. [3]
S.brasiliensis is commonly found in the soil and is saprophytic in its mycelium phase. The main vector of the pathogen is thought to be cats which spread the fungus through bites and scratches as well as lesions found on the bodies of cats. [2] [4] It is believed that the origin of the pathogen comes from the ingestion of rats by cats where it zoonotically spread to humans.
Sporothrix brasiliensis was first described in the Southeastern region of Brazil and sporotrichosis caused by the fungus was endemic to the region prior to 1990. However disease has quickly spread to other parts of Brazil and neighboring countries in South America with reported cases in Argentina, Paraguay, Bolivia, Columbia and Panama. [2] [5] A review in 2015 reported that of 5,814 cases of sporotrichosis in Brazil, 88% of cases were caused by S.brasiliensis. [6] The fungus has been isolated from intestinal and feline fecal samples which suggest that feces from infected cats may contaminate soil and contribute to the spread of the disease. [7]
Sporotrichosis is traditionally associated with subcutaneous exposure of Sporothrix propagules typically through minor injury while coming in contact with plants, soil, or organic matter. [8] However zoonotic transmission through cats mainly through scratching, biting, or coming in contact with skin lesions has been the main mode of transmission for S.brasiliensis, constituting the current epidemic in South America. [2] [4] While cutaneous infection is most common, pulmonary sporotrichosis from inhaling conidia, and disseminated sporotrichosis can also occur, primarily in individuals who are immunocompromised. [8] It is believed that S.brasiliensis is more virulent than other species that cause sporotrichosis like S.schenckii and results in larger, longer lasting lesion with a higher degree of local and systemic inflammation as demonstrated on mice. [1] A report in May 2020 reported a fatal case of pulmonary sporotrichosis caused by S.brasiliensis in a patient with no history of skin trauma or immunocompromise further supporting the notion of increased fungal virulence in S.brasiliensis relative to S.schenckii. [9]
Sporotrichosis caused by S.brasiliensis is difficult to treat due to resistance to main antifungal therapies. Current treatment recommendations for both felines and humans mainly include the antifungal drug itraconazole. [2] [7] Alternative therapies include the use of terbinafine and potassium iodine for cutaneous infection, and amphotericin B for severe pulmonary and disseminated forms of infection. [2]
While itraconazole has shown moderate effectiveness against S.brasiliensis, strains of the fungus that display resistance against the drug have been documented. [10] In addition, the treatment of felines is particularly difficult as care requires prolonged intervals of time daily and many cats fail to respond well to therapies. As such abandonment of treatments is frequent and typically occurs with the observed healing of skin lesions. [7] [11] Due to this the recurence of disease can typically occur with higher severity while increasing the chances of antifungal resistance strain development. Failure to complete treatment regimens also contributes to the continued spread of the disease to other cats and humans.
Botrytis cinerea is a necrotrophic fungus that affects many plant species, although its most notable hosts may be wine grapes. In viticulture, it is commonly known as "botrytis bunch rot"; in horticulture, it is usually called "grey mould" or "gray mold".
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.
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.
Sporotrichosis, also known as rose handler's disease, is a fungal infection that may be localised to skin, lungs, bone and joint, or become systemic. It presents with firm painless nodules that later ulcerate. Following initial exposure to Sporothrix schenckii, the disease typically progresses over a period of a week to several months. Serious complications may develop in people who have a weakened immune system.
Nakaseomyces glabratus is a species of haploid yeast of the genus Nakaseomyces, previously known as Candida glabrata. Despite the fact that no sexual life cycle has been documented for this species, N. glabratus strains of both mating types are commonly found. C. glabrata is generally a commensal of human mucosal tissues, but in today's era of wider human immunodeficiency from various causes, N. glabratus is often the second or third most common cause of candidiasis as an opportunistic pathogen. Infections caused by N. glabratus can affect the urogenital tract or even cause systemic infections by entrance of the fungal cells in the bloodstream (Candidemia), especially prevalent in immunocompromised patients.
Paracoccidioidomycosis (PCM), also known as South American blastomycosis, is a fungal infection that can occur as a mouth and skin type, lymphangitic type, multi-organ involvement type (particularly lungs), or mixed type. If there are mouth ulcers or skin lesions, the disease is likely to be widespread. There may be no symptoms, or it may present with fever, sepsis, weight loss, large glands, or a large liver and spleen.
Malassezia furfur is a species of yeast that is naturally found on the skin surfaces of humans and some other mammals. It is associated with a variety of dermatological conditions caused by fungal infections, notably seborrhoeic dermatitis and tinea versicolor. As an opportunistic pathogen, it has further been associated with dandruff, malassezia folliculitis, pityriasis versicolor (alba), and malassezia intertrigo, as well as catheter-related fungemia and pneumonia in patients receiving hematopoietic transplants. The fungus can also affect animals, including dogs.
Sporothrix schenckii, a fungus that can be found worldwide in the environment, is named for medical student Benjamin Schenck, who in 1896 was the first to isolate it from a human specimen. The species is present in soil as well as in and on living and decomposing plant material such as peat moss. It can infect humans as well as animals and is the causative agent of sporotrichosis, commonly known as "rose handler's disease." The most common route of infection is the introduction of spores to the body through a cut or puncture wound in the skin. Infection commonly occurs in otherwise healthy individuals but is rarely life-threatening and can be treated with antifungals. In the environment it is found growing as filamentous hyphae. In host tissue it is found as a yeast. The transition between the hyphal and yeast forms is temperature dependent making S. schenckii a thermally dimorphic fungus.
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.
Pseudocercosporella capsellae is a plant pathogen infecting crucifers. P. capsellae is the causal pathogen of white leaf spot disease, which is an economically significant disease in global agriculture. P. capsellae has a significant affect on crop yields on agricultural products, such as canola seed and rapeseed. Researchers are working hard to find effective methods of controlling this plant pathogen, using cultural control, genetic resistance, and chemical control practices. Due to its rapidly changing genome, P. capsellae is a rapidly emerging plant pathogen that is beginning to spread globally and affect farmers around the world.
Setosphaeria rostrata is a heat tolerant fungus with an asexual reproductive form (anamorph) known as Exserohilum rostratum. This fungus is a common plant pathogen, causing leaf spots as well as crown rot and root rot in grasses. It is also found in soils and on textiles in subtropical and tropical regions. Exserohilum rostratum is one of the 35 Exserohilum species implicated uncommonly as opportunistic pathogens of humans where it is an etiologic agent of sinusitis, keratitis, skin lesions and an often fatal meningoencephalitis. Infections caused by this species are most often seen in regions with hot climates like Israel, India and the southern USA.
Paracoccidioides brasiliensis is a dimorphic fungus and one of the two species that cause paracoccidioidomycosis. The fungus has been affiliated with the family Ajellomycetaceae although a sexual state or teleomorph has not yet been found.
Exophiala jeanselmei is a saprotrophic fungus in the family Herpotrichiellaceae. Four varieties have been discovered: Exophiala jeanselmei var. heteromorpha, E. jeanselmei var. lecanii-corni, E. jeanselmei var. jeanselmei, and E. jeanselmei var. castellanii. Other species in the genus Exophiala such as E. dermatitidis and E. spinifera have been reported to have similar annellidic conidiogenesis and may therefore be difficult to differentiate.
Dimorphic fungi are fungi that can exist in the form of both mold and yeast. This is usually brought about by change in temperature and the fungi are also described as thermally dimorphic fungi. An example is Talaromyces marneffei, a human pathogen that grows as a mold at room temperature, and as a yeast at human body temperature.
Pathogenic fungi are fungi that cause disease in humans or other organisms. Although fungi are eukaryotic, many pathogenic fungi are microorganisms. Approximately 300 fungi are known to be pathogenic to humans; their study is called "medical mycology". Fungal infections kill more people than either tuberculosis or malaria—about 2 million people per year.
Sporothrix is a ubiquitous genus of soil-dwelling fungus discovered by Schenck in 1898, and studied in more detail by Hektoen and Perkins. The first described and best known species is Sporothrix schenckii, the causative agent of rose handler's disease. New environmental, and pathogenic, species have been discovered with the potential for more to be found as molecular techniques advance.
Fonsecaea compacta is a saprophytic fungal species found in the family Herpotrichiellaceae. It is a rare etiological agent of chromoblastomycosis, with low rates of correspondence observed from reports. The main active components of F. compacta are glycolipids, yet very little is known about its composition. F. compacta is widely regarded as a dysplastic variety of Fonsecaea pedrosoi, its morphological precursor. The genus Fonsecaea presently contains two species, F. pedrosoi and F. compacta. Over 100 strains of F. pedrosoi have been isolated but only two of F. compacta.
Arthrographis kalrae is an ascomycetous fungus responsible for human nail infections described in 1938 by Cochet as A. langeronii. A. kalrae is considered a weak pathogen of animals including human restricted to the outermost keratinized layers of tissue. Infections caused by this species are normally responsive to commonly used antifungal drugs with only very rare exceptions.
Paracoccidioides lutzii is a dimorphic fungus that is one of the causal agents of paracoccidioidomycosis, together with Paracoccidioides brasiliensis. Unlike P. brasiliensis, which is found throughout Central and South America, P. lutzii is found only in Brazil and Ecuador. It is less virulent than P. brasiliensis.
Emmonsiosis, also known as emergomycosis, is a systemic fungal infection that can affect the lungs, generally always affects the skin and can become widespread. The lesions in the skin look like small red bumps and patches with a dip, ulcer and dead tissue in the centre.