Sporothrix brasiliensis

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Sporothrix brasiliensis
Scientific classification OOjs UI icon edit-ltr.svg
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.

Contents

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]

Morphology

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.

Hyphal Phase

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]

Yeast Phase

The yeast form of S.brasiliensis occurs at higher temperatures. Micro-morphologically the yeast takes the shape of an elongated cigar. [3]

Habitat and Ecology

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.

Epidemiology

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

Cutaneous lesions caused by sporotrichosis on cat's paw Feline sporotrichosis 3.jpg
Cutaneous lesions caused by sporotrichosis on cat's paw

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]

Treatment

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]

Structure of itraconazole Itraconazole.png
Structure of itraconazole

Issues with Treatment

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.

Related Research Articles

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<i>Candida albicans</i> Species of fungus

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<i>Aspergillus fumigatus</i> Species of fungus

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<span class="mw-page-title-main">Sporotrichosis</span> Medical condition

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.

<i>Nakaseomyces glabratus</i> Species of fungus

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<span class="mw-page-title-main">Paracoccidioidomycosis</span> Medical condition

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.

<i>Malassezia furfur</i> Species of fungus

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<i>Sporothrix schenckii</i> Species of fungus

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<i>Pseudocercosporella capsellae</i> Species of fungus

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.

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<span class="mw-page-title-main">Dimorphic fungus</span> Fungi that can exist as mold or yeast

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.

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<i>Fonsecaea compacta</i> Species of fungus

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.

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