Dermatologic Aspects of Actinomycosis Workup

Updated: May 07, 2018
  • Author: Talib Najjar, DMD, MDS, PhD; Chief Editor: Dirk M Elston, MD  more...
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Laboratory Studies

Culture findings in actinomycosis

Cultures from the lesions of actinomycosis typically reveal a variety of accompanying bacteria.

The most common bacterium found in association with actinomycosis is appropriately called Actinobacillus actinomycetemcomitans, which is an oral commensal organism that is common in the cervicofacial form of the disease.

Other bacteria include anaerobic streptococci, fusiform bacilli, Haemophilus species, and gram-negative bacilli, which appear to interact synergistically with Actinomyces species.

The associated bacteria in actinomycosis may help to establish an anaerobic medium that enhances the growth and propagation of the Actinomyces species.

Performing cultures for actinomycosis

To culture the actinomycosis specimen, flush the sulfur granules with sodium chloride solution to remove accompanying bacteria.

Incubate in a brain-heart agar plate in a 5% carbon dioxide atmosphere at 37°C for 4-6 days.

After approximately 2 days of incubation, the characteristic loose branching filaments of actinomycosis appear.

The colonies develop into an opaque mass within 4-6 days.

A israelii may be subcultured in a thioglycollate broth, in which it subsequently develops into hard granules with irregular borders.

Hematologic study results in actinomycosis

White blood cell counts are increased in approximately one half of patients; however, the white blood cell count can also be in the reference range.

Anemia may not be present, but superinfection is associated with normocytic and normochromic anemia.

An elevated erythrocyte sedimentation rate may be an associated finding.


Imaging Studies

Radiographic studies are useful in analyzing osseous involvement in actinomycosis because osteolysis is a common feature in patients with actinomycosis.

The radiographic appearance of actinomycosis lesions can range from that of a minor subperiosteal reaction and minimal rarefaction to that of classic osteomyelitis, with total lytic destruction or thickening and sclerosis that may be confused findings of a bone tumor. Bone is actively invaded by the infection, which results in localized areas of lytic bone destruction surrounded by areas of increased bone density. The sinus tracts may interconnect bony foci.


Other Tests

CT scanning and MRI are very helpful for detecting osseous and soft tissue involvement with persistent actinomycosis. [22]


Histologic Findings

The histologic feature of actinomycosis sulfur granules is pathognomic, which could be used as a tool to confirm the microbiologic findings.