Apophysomyces variabilis
| Apophysomyces variabilis | |
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| Scientific classification | |
| Kingdom: | Fungi |
| Division: | Zygomycota |
| Class: | Mucoromycotina |
| Order: | Mucorales |
| Family: | Saksenaeaceae |
| Genus: | Apophysomyces |
| Species: | A. variabilis |
| Binomial name | |
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Apophysomyces variabilis E.Àlvarez, Stchigel, Cano, D.A.Sutton & Guarro (2010) |
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Apophysomyces variabilis is an emerging fungal pathogen that can cause serious and sometimes fatal infection in humans. This fungus is a soil-dwelling saprobe with tropical to subtropical distribution. It is a zygomycete that causes mucormycosis, an infection in humans brought about by fungi in the order Mucorales. Infectious cases have been reported globally in locations including the Americas, Southeast Asia, India, and Australia.Apophysomyces variabilis infections are not transmissible from person to person.
Apophysomyces variabilis is one of four species in the genus Apophysomyces, which also includes A. elegans, A. ossiformis, and A. trapeziformis. In the past, Apophysomyces elegans was believed to be the species responsible for most cases of cutaneous mucormycosis attributed to Apophysomyces, but recently, some of the other species have been shown to be important in human infection. Since the new species have only recently been recognized, much remains to be learned about their relative clinical importance, comparative virulence, epidemiology, and anti-fungal drug susceptibilities.
Apophysomyces variabilis (CBS 658.93; FMR 10381) was first identified by Alvarez et al. in 2010 from a human osteomyelitis patient in the Netherlands Antilles. The genus Apophysomyces was first published in 1979 by Misra et al. who isolated A. elegans from soil in northern India. Apophysomyces variabilis was considered to be the same species as Apophysomyces elegans until September 2012 when Alvarez et al. determined that 16 strains of A. elegans were actually a complex of species in the genus Apophysomyces. Based on genetic, physiological, and morphological analyses, the authors concluded that the sixteen environmental and clinical strains of A. elegans could be divided in four clades corresponding to the species; A. elegans, A. trapeziformis, A. ossiformis, and A. variabilis. The species were differentiated based on the sporangiospore shape, sporangiophore type, and apophyseal shape. As well, carbon fixation ability aided in species differentiation with only A. elegans strains being able to assimilate the glycoside esculin. Alvarez et al. analysed three loci: the H3 gene, the internal transcribed spacer (ITS) regions of the nuclear rRNA gene, and the D1 and D2 domains of the 28S rRNA gene. This analysis resulted in a phylogeny containing the four clades. Interestingly, not one of the disease strains that had been identified as "A. elegans" clustered with taxonomically important strains of A. elegans in molecular phylogenetic analyses. Accordingly, the role of A. elegans (in the strict sense) as a human pathogen may warrant reconsideration.
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