''Sagenomella keratitidis'' is a

hyphomycete Hyphomycetes are a form classification of fungi, part of what has often been referred to as fungi imperfecti, Deuteromycota, or anamorphic fungi. Hyphomycetes lack closed fruit bodies, and are often referred to as moulds (or molds). Most hyphomy ...

discovered as its own species in 2008 by Sung-Yaon Hsieh et ''al.'' at the Institute of Plant and Microbial Biology and the

National Taiwan University Hospital The National Taiwan University Hospital (NTUH; ) is a medical facility located in the Zhongzheng District of Taipei, Taiwan. It started operations under Japanese rule in Daitōtei (today's Dadaocheng) on 18 June 1895, and moved to its present ...

History and taxonomy

Studies prior to 2009 showed evidence of fungal keratitis development with the use of contact lenses, but very little evidence of the development of keratitis associated with contact lens wear. Fungal keratitis associated with contact lens wear is quite rare when compared to microbial keratitis. Fungal keratitis accounts for only 5% of keratitides. The majority of '' Sagenomella'' species are soil-associated. ''S. keratitidis'' is the first species that is associated with the human eye. It was discovered in 2010 that ''Sagenomella'' can be grouped into three distinct categories, and these groups are not all descended from a common ancestor. DNA sequence analysis studies showed that ''S. keratitidis'' is most closely related to ''Sagenomella sclerotialis'' with two species showing 99% DNA homology. The researchers in Taiwan proposed the genus ''Sagenomella'' based on growth pattern and morphology.

Growth and morphology

''S. keratitidis'' has very slow growth on a range of cultures, making experiments involving isolation and purification very difficult. It has translucent, linked ameroconidia and very small conidiophores— its unusually small, few conidiophores are the reason why the colonies are white rather than gray. ''S. keratitidis'' species have spherical, phialidic conidia. ''Sagenomella'' species are closely related to ''

Acremonium ''Acremonium'' is a genus of fungi in the family Hypocreaceae. It used to be known as ''Cephalosporium''. Description ''Acremonium'' species are usually slow-growing and are initially compact and moist. Their hyphae are fine and hyaline, and p ...

'', but distinguished by their linked conidia. ''Sagenomella'' species are also distinguished from ''Acremonium'' species by their sharp-tipped, abruptly-ending conidia. ''S. keratitidis'' lacks chlamydospores. ''S. keratitidis'' may superficially resemble another member of its genus,''S.humicola'', under a microscope, but can be distinguished from ''S.humicola'' because of its extremely slow growth and lack of chlamydospores.

Physiology

The species of genus ''Sagenomella'' generally grow between the temperatures of 20-23 °C on malt extract agar, and are known for their slow growth. Little is known so far about the physiology of ''S. keratitidis'' but its close relative, ''S.chlamydospora'', grows best between a temperature of 37 °C and 40 °C, above which it does not survive. Ideal growth for ''Sagenomella'' species is at 27 °C.''S. keratitidis'' was found to grow better on media that had been modified with yeast.

Pathogenicity

''Sagenomella'' species normally cause unspecific symptoms and infections of ''Sagenomella'' are difficult to diagnose because this is an uncommon genus of fungus.''S. keratitidis'' was found to cause inflammation of the cornea, or

keratitis Keratitis is a condition in which the human eye, eye's cornea, the clear dome on the front surface of the eye, becomes inflammation, inflamed. The condition is often marked by moderate to intense pain and usually involves any of the following sy ...

, in an individual who wore contact lenses. So far, this has been the only case of keratitis found to be caused by ''S. keratitidis''.''S. keratitidis'' is not as pathogenic as other members of the same genus, such as ''S.chlamydospora'', which can cause serious

mycosis 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 ...

in canines. Canine ''S.chlamydospora'' infections can cause the animal to limp, experience pain in its spine, and feel a general lack of energy. If left untreated, these infections can spread to humans.

Habitat and ecology

''S. keratitidis'' is a human eye pathogen, unlike its other genus counterparts, whose habitat is either soil, manure, or fodder. Although rare, it may occur due to poor sanitation in individuals who wear contact lenses.

References

{{Taxonbar, from=Q28868579 Trichocomaceae Fungi described in 2009 Fungus species