Actinomycosis
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A "sulfur granule" is a colony of filamentous bacteria surrounded by and coated with neutrophils.

* Dedicated to Thomas Bond Jr., MD, of Baltimore, Maryland -- Father of Oral Pathology
New Editor: J. E. Bouquot, D.D.S., M.S.D., Director of Research, The Maxillofacial Center
165 Scott Avenue, Suite 100, Morgantown, WV 26508,  MFCenter@aol.com

Actinomycosis

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Actinomycosis is an infection by filamentous, branching, gram-positive anaerobic bacteria of the Actinomyces species.  Actinomycetes are normal saprophytic micro-organisms of the mouth which  prefer to live in the gingival sulcus (especially in periodontal pockets), in dental plaque and calculus, and in the tonsillar crypts.  Up to 40% of surgically removed hyperplastic tonsils, in fact, will show one or more colonies of Actinomyces, sometimes forming colonies large enough and firm enough to appear like yellowish grains of rice.  Actinomyces israelii is most often associated with head and neck infections, but others have also produced actinomycosis if this region, including: A. naeslundii, A. viscosus, A. odontolyticus, A. meyeri and A. bovis.  Arachnia propionica can also produce actinomycosis.  Regardless of the species involved, the micro-organism is almost always synergistically combined with streptococci and staphylococci.  

Clinical Features. Actinomycosis may     

Histopathology and Differential Diagnosis. The diagnosis of actinomycosis depends of the presence of one or more microcolonies (sulfur granules) of filamentous bacteria, often admixed with cocci.  The central core of the colony is composed of basophilic filaments while the periphery has filamentous and club-like eosinophilic structures (micro-organisms) extending perpendicular to the surface and covered by neutrophils.  This eosinophilic peripheral layer is sometimes referred to as the Splendore-Hoeppli phenomenon.  Ultimately, the diagnosis should be confirmed by culture.  Fungus stains such as methenamine silver should be used in addition to Brown-Brenn or Gram-Weigert stains, because they also stain filamentous bacteria.  Actinomycosis granules, including Nocardia granules, consist of delicate, branched, gram-positive filaments 1 µm thick.

The colonies are typically floating in a pool of pus with intermixed fragments of edematous granulation tissue containing variable numbers of chronic and acute inflammatory cells.  Jawbone actinomycosis is most often found in the walls of a periapical cyst or as part of a fistulating periapical granuloma.

The differential diagnosis of actinomycosis granules include Nocardia, eumycotic mycetoma and botryomycosis (S. aureaus, Pseudomonas, E. coli, Proteus vulgaris, Streptococci).  The granules of eumycotic mycetomas are composed of branched, septate, sometimes brown-pigmented hyphae.  Nocardia colonies are not as dense as actinomycosis colonies, instead forming a loose network of intertwining branches with scattered inflammatory cells between instead of forming a thick coat on the colony surface.  A modified acid-fast stain is useful to distinguish actinomycetes from the bacilli of Nocardia, which are weakly acid-fast (actinomycetes are negative).  Granules of botryomycosis are composed either of gram-positive cocci or gram-negative bacilli.

Treatment and Prognosis. Cervicofacial actinomycosis of short duration typically responds well to a 6 week course of high-dose penicillin, in addition to abscess drainage and excision of the sinus tract.  In vivo resistance to penicillin has not yet been reported but because in vitro resistance has been seen some authors recommend tetracycline, which is as effective as penicillin.  More deep-seated or long-term cases may required up to a year of antibiotic therapy, with part of that being intravenous therapy.  The more typical actinomycosis-associated odontogenic and periodontal abscesses of the mouth and jaws often respond well to surgical removal of infected tissue and a 2-3 week course of high-dose penicillin.           

References (Chronologic Order)

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General references:

Neville BW, Damm DD, Allen CM, Bouquot JE. Oral and maxillofacial pathology. Philadelphia, W. B. Saunders; 1995.

Elder D, Elenitsas R, Jaworsky C, Johnson B Jr. Lever's Histopathology of the skin, 8th edition. Philadelphia; Lippincott-Raven, 1997.

Sapp JP, Eversole LR, Wysocki GP. Contemporary oral and maxillofacial pathology. Mosby; St. Louis, 1997.

Odell EW, Morgan PR. Biopsy pathology of the oral tissues. London; Chapman & hall Medical, 1998.

Specific references:

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