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Dermatologic Aspects of Actinomycosis Workup

  • Author: Talib Najjar, DMD, MDS, PhD; Chief Editor: Dirk M Elston, MD  more...
Updated: Jun 27, 2016

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.[21]


Histologic Findings

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

Contributor Information and Disclosures

Talib Najjar, DMD, MDS, PhD Professor of Oral and Maxillofacial Surgery and Pathology, Rutgers School of Dental Medicine

Talib Najjar, DMD, MDS, PhD is a member of the following medical societies: American Society for Clinical Pathology

Disclosure: Nothing to disclose.

Specialty Editor Board

Michael J Wells, MD, FAAD Associate Professor, Department of Dermatology, Texas Tech University Health Sciences Center, Paul L Foster School of Medicine

Michael J Wells, MD, FAAD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Dermatology, American Medical Association, Texas Medical Association

Disclosure: Nothing to disclose.

Drore Eisen, MD, DDS Consulting Staff, Department of Dermatology, Dermatology Research Associates of Cincinnati

Drore Eisen, MD, DDS is a member of the following medical societies: American Academy of Dermatology, American Academy of Oral Medicine, American Dental Association

Disclosure: Nothing to disclose.

Chief Editor

Dirk M Elston, MD Professor and Chairman, Department of Dermatology and Dermatologic Surgery, Medical University of South Carolina College of Medicine

Dirk M Elston, MD is a member of the following medical societies: American Academy of Dermatology

Disclosure: Nothing to disclose.

Additional Contributors

Janet Fairley, MD Professor and Head, Department of Dermatology, University of Iowa, Roy J and Lucille A Carver College of Medicine

Janet Fairley, MD is a member of the following medical societies: American Academy of Dermatology, American Federation for Medical Research, Society for Investigative Dermatology

Disclosure: Nothing to disclose.


Many thanks for continuous help and advice from doctor Edward Jonson, MD, internationally known infectious diseases specialist and Dean, Trinity School of Medicine and Caribbean Studies, Saint Vincent.

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Photomicrograph of gram-positive organisms in actinomycosis, which may be confused with those causing a mycotic infection (hematoxylin and eosin, original magnification X40).
Photomicrograph of a characteristic sulfur granule of actinomycosis (hematoxylin and eosin, original magnification X10).
Diagram of potential oral anaerobic infection.
Image shows an oral fistula caused by actinomycosis.
Periapical radiograph shows infection in the premolar tooth.
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