Actinomadura Species

Actinomadura is an aerobic actinomycetes.

Actinomadura is a filamentous bacterium found in soil. Although it was once believed to be a fungus, the information later attained about its ultrastructural cellular properties showed that Actinomadura is in fact an aerobic actinomycetes. However, for the reason that most of the diagnostic procedures related to Actinomadura are still held in mycology laboratories in many centers, the discussion on Actinomadura is included in this website.

Actinomadura madurae, Actinomadura pelletieri, and Actinomadura dassonvillei are the species included in the genus Actinomadura. Actinomadura madurae is distinguished from A. pelletieri by its ability to produce acid from cellobiose.

It is one of the common causes of actinomycotic mycetoma (maduramycosis or madura foot), characterized by formation of granules containing branched filaments. It is a chronic infection involving the subcutaneous tissue, muscles and bones particularly of lower extremities. The characteristic granules formed during the course of infection drain via formation of sinuses.

The growth rate of Actinomadura is slow. It grows on routine mycologic or mycobacteriologic media and under aerobic conditions. The colony has a glabrous, waxy, membranous or mucoid, heaped and folded appearance. The color of the colony is red, pink, yellow, orange, white, or tan. Following two weeks of incubation, aerial hyphae may develop on the surface, particularly on Lowenstein-Jensen medium [1295].

Actinomadura is Gram positive and nonacid-fast. The typical structures are the filaments which are nonfragmenting and narrow (0.5-1 µm in diameter). These filaments branch abundantly. Chains of round conidia may occasionally be produced from the aerial hyphae, particularly on slide cultures [1295].

The granules of Actinomadura are 0.1 to several mm in diameter. They are composed of branching, beaded, Gram positive filaments which are delicate and around 1 µm in diameter [462].

Nocardia, Nocardiopsis, and Streptomyces.

Some of the properties related to the microscopic features and growth of the aerobic actinomycetes are summarized in the Table below. The color and texture of the colony, hydrolysis of casein, tyrosine, xanthine, gelatin, starch, and urea, and acid formation from lactose, xylose, and cellobiose should also be examined for definitive identification of these bacteria at species level [1295].

STRUCTURE/PROPERTY	DIFFERENTIATION
Acid fast staining	Actinomadura (-) Nocardiopsis (-) Streptomyces* (-) Nocardia (+)
Spontaneous fragmentation of hyphae	Actinomadura (-) Streptomyces (-) Nocardia (+) Nocardiopsis (+)
Ability to grow in existence of lysozyme	Actinomadura (-) Nocardiopsis (-) Streptomyces** (-) Nocardia (+)

*The spores of some Streptomyces spp. may be acid fast.
**Some strains may grow.

No special precautions other than general laboratory precautions are required.

Treatment regimens usually consist of a combination therapy. Since mycetoma may be caused by several different fungi or aerobic actinomycetes, identification of the causative agent and differentiation of eumycotic mycetoma from actinomycotic mycetoma constitute the major points in application of appropriate antimicrobial therapy. While Actinomadura madurae is usually suceptible to a combination of streptomycin and dapsone, Actinomadura pelletieri responds better to a combination of streptomycin and trimethoprim-sulfamethoxazole. As well as antimicrobial therapy, surgery (limited and bulk-reduction surgery, preferentially) is required for some patients.

PubMed

GenBank

Culture of actinomadura spp.

References

462. Collier, L., A. Balows, and M. Sussman. 1998. Topley & Wilson's Microbiology and Microbial Infections, 9th ed, vol. 4. Arnold, London, Sydney, Auckland, New York.

1295. Larone, D. H. 1995. Medically Important Fungi - A Guide to Identification, 3rd ed. ASM Press, Washington, D.C.