Sagenomella keratitidis
| Sagenomella keratitidis | |
|---|---|
| |
| Scientific classification | |
| Kingdom: | |
| Division: | |
| Class: | |
| Order: | |
| Family: | |
| Genus: | |
| Species: | S. keratitidis
|
| Binomial name | |
| Sagenomella keratitidis Sung-Yaon Hsieh et al. (2009)
| |
Sagenomella keratitidis is a hyphomycete 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.[1]
History and taxonomy[edit]
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.[1] Fungal keratitis associated with contact lens wear is quite rare when compared to microbial keratitis. Fungal keratitis accounts for only 5% of keratitides.[2] The majority of Sagenomella species are soil-associated. S. keratitidis is the first species that is associated with the human eye.[1] 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.[3] DNA sequence analysis studies showed that S. keratitidis is most closely related to Sagenomella sclerotialis with two species showing 99% DNA homology.[1] The researchers in Taiwan [1] proposed the genus Sagenomella based on growth pattern and morphology.[1]
Growth and morphology[edit]
S. keratitidis has very slow growth on a range of cultures, making experiments involving isolation and purification very difficult.[1] It has translucent, linked ameroconidia[1] and very small conidiophores— its unusually small, few conidiophores are the reason why the colonies are white rather than gray.[1] S. keratitidis species have spherical, phialidic conidia.[1][3] Sagenomella species are closely related to Acremonium, but distinguished by their linked conidia.[4] Sagenomella species are also distinguished from Acremonium species by their sharp-tipped, abruptly-ending conidia.[4] S. keratitidis lacks chlamydospores.[1] 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.[1]
Physiology[edit]
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.[4] 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.[5] Ideal growth for Sagenomella species is at 27 °C.[4]S. keratitidis was found to grow better on media that had been modified with yeast.[1]
Pathogenicity[edit]
Sagenomella species normally cause unspecific symptoms and infections of Sagenomella are difficult to diagnose because this is an uncommon genus of fungus.[5]S. keratitidis was found to cause inflammation of the cornea, or keratitis, in an individual who wore contact lenses.[1] So far, this has been the only case of keratitis found to be caused by S. keratitidis.[1]S. keratitidis is not as pathogenic as other members of the same genus, such as S.chlamydospora, which can cause serious mycosis in canines.[5] 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.[5]
Habitat and ecology[edit]
S. keratitidis is a human eye pathogen, unlike its other genus counterparts, whose habitat is either soil, manure, or fodder.[1] Although rare, it may occur due to poor sanitation in individuals who wear contact lenses.[1]
References[edit]
- ^ a b c d e f g h i j k l m n o p q Hsieh, Huei-Mei; Ju, Yu-Ming; Hsueh, Po-Ren; Lin, Hsiu-Yi; Hu, Fung-Rong; Chen, Wei-Li (2009). "Fungal keratitis caused by a new filamentous hyphomycete Sagenomella keratitidis". Botanical Studies. 50: 331–335.
- ^ Khor, Wei-Boon; Aung, Tin; Saw, Seang-Mei; Wong, Tien-Yin; Tambyah, Paul; Tan, Ai-Ling; Beuerman, Roger; Lim, Li; Chan, Wing-Kwong; Heng, Wee-Jin; Lim, Jimmy; Loh, Raymond SK; Lee, Sao-Bing; Tan, Donald (2006). "An Outbreak of Fusarium Keratitis Associated With Contact Lens Wear in Singapore". JAMA. 295 (24): 2867–73. doi:10.1001/jama.295.24.2867. PMID 16804153.
- ^ a b Sigler, Lynne; Sutton, Deanna; Gibbas, Connie Fe C; Summerbell, Richard; Noel, Rhonda; Iwen, Peter (2010). "Phialosimplex, a new anamorphic genus associated with infections in dogs and having phylogenetic affinity to the Trichocomaceae". Medical Mycology. 48: 335–345. doi:10.3109/13693780903225805. PMID 20141373.
- ^ a b c d Gams, W (1978). "Connected and disconnected chains of phialoconidia and Sagenomella gen. nov. segregated from Acremonium". Persoonia. 10: 97–112.
- ^ a b c d Gené, Josepa; Blanco, Jose; Cano, Josep; García, Marta; Guarro, Josep (2003). "New Filamentous Fungus Sagenomella chlamydospora Responsible for a Disseminated Infection in a Dog". J. Clin. Microbiol. 41 (4): 1722–5. doi:10.1128/jcm.41.4.1722-1725.2003. PMC 153912. PMID 12682169.