Some of the more frequently encountered aerobic actinomycetes (eg, Nocardia and Streptomyces) have a distinct earthy or musty odor. For safety reasons, it is never acceptable to sniff directly from an agar plate. However, the indirect wafting odor of a damp basement may be evident.
Specimens sent to the microbiology laboratory for the culture of suspected actinomycetes should be marked as such. Cultures must be held longer than 48 hours (and preferably for at least 14 days). These organisms grow slowly. The clinician should always consult the microbiology laboratory when such organisms are suspected.
It may not be necessary for the microbiology laboratory to provide identification of the genus to the species level for a good clinical outcome. Genus identification may be all that is required, in addition to susceptibility testing. Full identification may only be necessary in cases where epidemiological data is required.
Specimen preparation
Always check for clumps or granules; crush any found. While preparing slides and inoculating media, process patient specimens accordingly:
- Sputum, bronchial washings, exudates (spread evenly)
- Body fluids (centrifuge at 3000g for 20 minutes - use the sediment)
- Tissue (cut, grind tissue; use a tissue homogenizer)
