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MICROBIOLOGY LEGEND
CYCLE 31 ORGANISM 2
Actinomycosis
Actinomycosis is a rare type of bacterial infection. Most bacterial infections are confined to one part of the body because the bacteria are unable to penetrate through the body’s tissue. However, actinomycosis is unusual in that the infection is able to move slowly but steadily through the body’s tissue. The bacteria that have been reported to cause actinomycosis in humans include Actinomyces israelii, A. naeslundii, A odontolyticus, A gerencseriae, A viscosus. A. meyeri, A. georgiae. A. neuii subsp.neuii, P. propionicum and B. dentium. These bacteria are part of the normal flora of the mouth, and many of them can be found in the genitourinary tract. A. israelii is the most common species in clinical infections. However actinomycosis (with lesions in tissue) is currently rare.
Symptoms of actinomycosis include: swelling and inflammation of affected tissue tissue damage that results in scar tissue formation of abscesses (pus-filled swellings) small holes or tunnels that develop in tissue and leak a type of lumpy pus
Sites of infection: Oral cervico-facial ("lumpy jaw") Pelvic infection (IUD-associated) Thoracic: pneumonia, mass lesion (may be confused with malignancy) Intra-abdominal: abscess or mass lesion Musculoskeletal Osteonecrosis of jaw: post chemotherapy Cardiac: endocarditis (The "A" of HACEK, Actinobacillus actinomycetemcomitans [Aggregatibacter actinomycetemcomitans]) CNS: meningitis, encephalitis, brain abscess Disseminated (rare)
The three clinical types of Actinomyces infection are cervicofacial, thoracic, and abdominal. The Actinomyces species act as opportunistic pathogens and normally do not cross normal human mucosal borders. However, in cases of low tissue oxygen tension or mucosal disruptions, as with an appendectomy, actinomycosis can result. Pelvic actinomycosis normally begins as a subacute or chronic disease months or years before a patient presents herself to a physician.
Thistle QA is a SANAS accredited organisation, No: PTS0001 Accredited to ISO guide 43 and ILAC G13 Certificate available on request or at www.sanas.co.za
P.O. Box 131375, Bryanston, 2074
Ground Floor, Block 5 Bryanston Gate, 170 Curzon Road Bryanston, Johannesburg, South Africa
804 Flatrock, Buiten Street, Cape Town, 8001
www.thistle.co.za Tel: +27 (011) 463 3260 Fax: +27 (011) 463 3036 Fax to Email: + 27 (0) 86‐538‐4484 e‐mail : [email protected] Usually, the symptoms include lower abdominal pain, cachexia, vaginal discharge, and nausea. Hydronephrosis due to urethral compression by the pelvic abscess can also be an abnormality. As the disease progresses, it can become severe, with tubo-ovarian abscess formation leading to a “frozen pelvis” and mimicking pelvic cancer. Infections of the female genital tract with Actinomyces can be caused by surgery, perforation of the bowel, or foreign bodies, such as IUDs. Actinomycosis in association with an IUD usually involves the pelvis, and patients present with symptoms similar to the symptoms of salpingo-oophoritis, tubo-ovarian abscess, or pelvic abscess .
Laboratory Identification In Gram-Stained smears prepared from lesions, one may observe characteristic sulphur granules, which are granular micro colonies of the organism surrounded by purulent exudate. The cells of A. israelii are gram-positive rods, usually 1 µm in diameter, but they are extremely variable in length. The cells may be short diphtheroid rods, club shaped, branched, or unbranched filaments. Rough colonies composed of branched rods or filaments usually develop slowly on blood agar. Young colonies (2 to 3 days old), when viewed with the dissecting microscope, appear as thin radiating filaments known as spider colonies. When the colonies get to be about 7 to 14 days old, they are often raised, heaped up, white, opaque, and glistening; have irregular or labate margins; and are called molar tooth colonies. However, smooth strains (about one third of A. israelii) produce colonies more rapidly than rough strains. Smooth strains may produce 1mm to 2 mm circular, slightly raised white, opaque, smooth glisteing colonies after only 2 to 3 days of incubation.
A. naeslundii may also produce smooth or rough colonies. Colonies of A. viscosus are most often 0.5mm to 2mm in diameter, entire , convex grayish, and translucent. In A. odontolyticus colonies, a red color may develop on blood agar after 7 to 14 days of anaerobic incubation or after the plates have been left out in room air at ambient temperature for several days.
Actinomyces odontolyticus: Smooth red colony Gram Stain of Actinomyces
Besides morphology, colony characteristics, and metabolic products, characteristics useful for identification of the actinomycetes include relationship to oxygen, appearance and rapidity of growth in enriched thioglycolate medium, indole production, esculin and gelatin hydrolysis, fermantation of certain carbohydrates, results of testing with several rapid enzyme tests, 16SrRNA sequencing and other molecular methods.
Treatment Treatment of actinomycosis usually requires antibiotics for several months to a year. Surgical drainage or removal of the lesion may be needed. If the condition is related to an IUD, the device must be removed.
References 1. Koneman's color atlas and textbook of diagnostic microbiology - By Washington C. Winn, Elmer W. Koneman ______Questions 1. Discuss the morphological characteristics of Actinomyces. 2. Discuss the types of Actinomyces infections. 3. Discuss the treatment of Actinomycosis. ______
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