There are over 75 species of Actinomadura, but only two are of major clinical significance.
The Actinomadura were originally classified as Nocardia. Most infections present as an initial painless nodule in the skin of the foot. The foot is commonly implicated from walking barefoot and stepping on soil or debris. Infections are most common in tropical areas among people walking barefoot. Nodules lead to sinus tract formation, then fibrous tissue formation. Areas become deformed and may progress to muscle and bone involvement.
Table 5. Characteristics of Actinomadura species.
| Characteristics | Comments |
| Appearance on Gram stain | Gram-positive, filamentous, intertwining, branched filaments with short spore chains; straight, hooked, or irregular spirals;31 short or long chains of arthrospores when mature |
| Appearance on modified acid-fast stain (MAS) | Not acid-fast |
| Most often associated with clinical disease | Actinomadura madurae and Actinomadura pelletieri |
| Colonial growth | Aerial mycelium with blue, brown, cream, gray, green, pink, red, white, or yellow color;31 colonies are mucoid, wrinkled, and have molar tooth appearance |
| Phenotypic Characterization31 | - Casein hydroyzed; may also hydrolyze hypoxanthine and tyrosine
- A. pelletieri are assacharolytic producing acid from glucose and trehalose
- A. madurae produces acid from adonitol, arabinose, cellobiose, mannitol, trehalose, xylose, glycerol, mannose, mannitol, rhamnose
- A. madurae hydrolyzes esculin, A. pelletieri does not
- Lysozyme resistance negative
- Urea hydrolysis negative
- Nitrate reduction positive
|
| Temperature of Optimal Growth31 | Optimal temperature range 10–60°C |
31. National Health Service. (2016). UK standards for microbiology investigations: Identification of aerobic actinomycetes. The Royal College of Pathologists. https://www.rcpath.org/static/ce08d742-b58e-4e8d-986c43a75ac367c3/uk-smi-id-10i2-2-identification-of-aerobic-actinomycetes-october-2016-pdf.pdfFigure 22. CDC/Hardin. (1965). Image #14748. Under a magnification of 900X, this photomicrograph of a Gram-stained unidentified tissue specimen, revealed some of the ultrastructural histopathology associated with an actinomycotic mycetoma, due to the Gram-positive bacterium, Nocardia madurae [Note: now referred to as Actinomadura madurae]. PHIL public domain. https://phil.cdc.gov/Details.aspx?pid=14748
Figure 23. CDC/Ajello. (1968). Image #21188. This photograph depicted a Petri dish culture plate that contained an unidentified medium, which had been inoculated with what was described, as a Texas isolate of an Actinomadura pelletieri, formerly known as Nocardia pelletieri sample, and subsequently gave rise to this colony. This colony was pinkish-red in color, highly wrinkled, and asymmetrical in its morphology. PHIL public domain. https://phil.cdc.gov/Details.aspx?pid=21188
