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School of Molecular & Biomedical Science
THE UNIVERSITY OF ADELAIDE
AUSTRALIA 5005

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Dr David Ellis

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Rhizopus sp.

The genus Rhizopus is characterized by the presence of stolons and pigmented rhizoids, the formation of sporangiophores singly or in groups from nodes directly above the rhizoids, and apophysate, columellate, multi-spored, generally globose sporangia. After spore release the apophyses and columella often collapse to form an umbrella-like structure. Sporangiospores are globose to ovoid, one-celled, hyaline to brown and striate in many species. Colonies are fast growing and cover an agar surface with a dense cottony growth that is at first white becoming grey or yellowish brown with sporulation.


Culture of Rhizopus oryzae.

 

MIC data is limited.  Antifungal susceptibility testing of individual strains is recommended.

Antifungal MIC ug/mL Antifungal
MIC ug/mL
Range
MIC90
Range
MIC90
Itraconazole
0.25-8
4
Amphotericin B
0.03-4
2
Voriconazole
4->64
>64
Posaconazole
0.03-8
2

 

Clinical significance:

Rhizopus oryzae (=R. arrhizus) is the most common causative agent of zygomycosis, accounting for some 60% of the reported culture positive cases, and nearly 90% of the rhinocerebral forms of infection. R. oryzae has a world-wide distribution with a high prevalence in tropical and subtropical regions. It has been isolated from many substrates, including a wide variety of soils, decaying vegetation, foodstuffs, and animal and bird dung. R. oryzae is often used in the production of fermented foods and alcoholic beverages in Indonesia, China and Japan. However, it also produces the ergot alkaloid agroclavine which is toxic to humans and animals.

Rhizopus oryzae description

 

Differentiation of pathogenic Rhizopus microsporus group isolates.

Species
Growth
at 45 C
Growth
at 50 C
Main species characteristics

R. azygosporus

Good
No
Abundant azygospores.

R. microsporus var.
microsporus

Good
No
Sporangiospores angular to ellipsoidal and distinctly striate, up to 5–6 µm diam.

R. microsporus var.
oligosporus

Restricted
No
Sporangiospores globose, up to
9 µm diameter or more, heterogeneous.

R. microsporus var.
rhizopodiformis

Good
Good
Sporangiospores globose rarely over 5 µm in diameter minutely spinulose.

R. schipperae

Good
No
Abundant chlamydospores and restricted sporulation.

 

Mycosis: Zygomycosis

Further reading:

Domsch, K.H., W. Gams, and T.H. Anderson. 1980. Compendium of soil fungi. Volume 1. Academic Press, London, UK.

Ellis, D.H. 1997. Zygomycetes. Chapter 16 In Topley and Wilson's Microbiology and Microbial Infections. 9th edition Edward Arnold London pp247-277.