Actinomycosis is caused by various bacterial species of the actinomycete group. Usually, the disease is caused by Actinomyces israelii, an anaerobic gram-positive organisms that enters the tissue through a break in the mucosa (Eastridge, 1972). The Actinomyces genus of bacteria includes other species that normally inhabit the oral cavity but are seldom pathogenic. The infection begins as an inflammatory soft tissue mass, which can enlarge into an abscesslike swelling, with penetration of the overlying skin and the development of recognizable draining fistulae.
The term actinomycosis is misleading. Because of the derivative term mycosis (from the Greek mykes), some believe that actinomycosis is a fungal infection, although it is not a fungal infection. Aktino referred to the radiating organism in the sulfur granule as ray fungus. Human actinomycosis was first described in the medical literature in 1857, although a similar disease in cattle had been described in 1826. In 1877, Bollinger found Actinomyces bovis in granules from cattle with a condition called lumpy jaw. In 1878, Israel discovered granules in human autopsy material and described actinomycosis in humans in 1885 (Richtsmeier, 1979). Israel further discovered that Actinomyces species do not survive outside mammalian hosts and that they are not found exogenously in plants or soil.
Prior to the antibiotic era, actinomycosis was a common illness and easily recognized at clinical examination. However, the microbiologic features of the etiologic organisms were not fully clarified until the 1940s (Erikson, 1940). The therapeutic outcome of surgical management was variable, and even if healing occurred, sequelae and complications were common (Waksman, 1943; Georg, 1974). The disease often became lifelong, and death was not unusual. At the dawn of the antibiotic era, morbidity resulting from actinomycosis decreased, and a general lack of familiarity with the disease process resulted (Brock, 1973). Subsequently, diagnoses of actinomycosis were often delayed because of a lack of microbiologic techniques.
strong>Pathophysiology: The pathogen is a filamentous bacterium. Historically, actinomycosis has been confused with a fungal disease because of its appearance and the slowly progressive nature of the lesions, which mimics mycotic illness. Confusion was so great that, for many years, some investigators placed Actinomyces species in an intermediate status between fungi and bacteria (Eastridge, 1972). The unique nature of the organism is the absence of a nuclear membrane, which places Actinomyces species among the higher prokaryotic bacteria. The lack of chitin and gluten, coupled with the presence of muramic acid in the cell walls and the absence of mitochondria, is another distinct feature (Behbehani, 1983).
All species of Actinomyces are normal commensal inhabitants of the oral and buccal cavities in humans and certain other mammals. They cannot be classified as symbiotic organisms because they do not have a mutually beneficial relationship with their host. They are not true parasites because they usually do not cause harm to the host; however, they definitely assume a parasitic role when they result in an infection with an inflammatory tissue response. Similar to Mycobacterium tuberculosis, actinomycetes survive phagocytosis by host cells, and they may be characterized as facultative intracellular parasites.
Actinomycosis does not appear to be an opportunistic infection because it is not common in patients who are immunosuppressed or in patients with AIDS. One of the authors has experience in producing a bone infection in animals that leads to osteomyelitis; however, actinomycosis could not be induced in the tibias and mandibles of rabbits. This outcome may have been the result of the avirulent nature of the organisms. Perhaps the presence of other infectious bacteria is required in addition to the Actinomyces species to initiate the infection in experimental models (Najjar, 1980).
Frequency:
- In the US: The incidence of human actinomycosis has been decreasing in the United States. Weese and Smith reported prevalences of 1 case per 12,000 admissions in the 1930s and 1 case per 21,000 admissions in the 1950s. Bennhoff reported a prevalence of only 1 case per 63,000 admissions in the 1970s. Actinomycosis can still be found in inner-city populations of the United States.
- Internationally: Actinomycosis remains a problem in underdeveloped countries (Coleman, 1969).
Mortality/Morbidity: No evidence of long-term morbidity is observed in patients treated with antibiotics and surgical excision of the necrotic tissue.
Race: Actinomycosis affects persons of all socioeconomic levels and all races, and the disease is not limited to any single segment of the population.
Sex: A male-to-female predominance in a ratio of approximately 3:1 has been observed (Eng, 1981). This predominance is postulated to reflect the greater likelihood for facial and oral trauma and the lack of oral hygiene in males compared with females.
Treatment
Medical Care: The presence of associated bacteria appears to be fundamental to the development of clinical infection. Therefore, antibiotic coverage should be aimed at all associated organisms in patients with actinomycosis. An aerobic environment is an unfavorable condition for the growth of Actinomyces species and thus halts the infection (Schaal, 1983; Lewis, 1978; Hennrikus, 1987; Lerner, 1974; Deshpande, 1985).
With the combined use of penicillin and surgery, cure has become the rule rather than the exception.
- The treatment of choice includes large doses of antibiotics and prolonged therapy coupled with drainage of the abscesses or radical excision of the sinus tracts. High penicillin concentrations are necessary to penetrate areas of fibrosis and suppuration and possibly the granules themselves. Occasionally, extensive disease may respond to intravenous penicillin alone, rendering surgery unnecessary.
- If recognized early, cervicofacial infection has an excellent prognosis with the use of antibiotics alone. In the treatment of this infection, tetracyclines are as effective as penicillin. Intravenous penicillin G (10-20 million U/d for 2-6 wk) followed by oral penicillin (2-4 g/d for an additional 3-12 mo) is the typical therapy for the most deep-seated infections (Holmberg, 1977).
- Actinomyces organisms are also susceptible to chloramphenicol, erythromycin, tetracyclines, and clindamycin but not to metronidazole or aminoglycosides.
- When tuberculosis is suspected, the effects of rifampin therapy can mask the signs of undiagnosed pulmonary actinomycosis.
- Because the bacterial species do not vary in terms of their susceptibility to first-line drugs (eg, penicillin, tetracyclines, erythromycin, first-generation parenteral cephalosporins, clindamycin), infection with strains other than A israelii should also respond to adequate courses of treatment with penicillin G or any of its alternatives. Serum concentrations of sulfonamides (4-8 mg/dL) inhibit some strains of A israelii; therefore, proven cases of actinomycosis (that are not mistaken instances of nocardiosis) may occasionally respond to sulfonamides. Oral cephalosporins and semisynthetic penicillins (eg, oxacillin, dicloxacillin) are less active in vitro and are best avoided (Boand, 1949).
- The acquired resistance of Actinomyces species to antimicrobials, particularly to penicillin G, has not been confirmed in vivo. When the response to penicillin is poor, consider an undrained abscess or an associated infection with a resistant bacterium. European investigators favor the use of ampicillin for initial therapy because associated bacteria are less susceptible to penicillin G in vitro, and they use metronidazole or clindamycin as a secondary agent when Bacteroides fragilis or Bacteroides thetaiotaomicron is present. Imipenem produces an impressive response in extensive, complicated, and relapsing abdominothoracic infections that fail to respond to several surgical procedures and trials of penicillin G (Edelmann, 1987).
Surgical Care: Surgical management has consisted of various treatment modalities, including excision of sinus tracts, drainage of the abscess cavities, removal of the bulky infected masses, and irrigation and curettage of the osteomyelitic bony lesions.
The abscesses should be drained, or sinus tracts should be radically excised. With the combined use of penicillin and surgery, cure has become the rule rather than the exception.
Medication
The goals of pharmacotherapy in the treatment of actinomycosis are to eradicate the infection, reduce morbidity, and prevent complications.
Drug Category: Antibiotics -- Therapy must cover all likely pathogens in the context of this clinical setting. Antibiotic selection should be guided by blood culture sensitivity whenever feasible.
| Drug Name | Penicillin G (Pfizerpen) -- Interferes with synthesis of cell wall mucopeptide during active multiplication, resulting in bactericidal activity against susceptible microorganisms. Prolonged therapy, including >1 year, may be necessary. |
|---|---|
| Adult Dose | Cervicofacial: 1-6 million U/d IV for 2-6 wk Thoracic and abdominal: 10-20 million U/d IV (administer slowly) for 2-6 wk; administer penicillin VK thereafter |
| Pediatric Dose | <1> 1-4 weeks: 25,000 U q8h IV (1.2-2 kg) or q6h (>2 kg) <12>1 month: for mild/mod disease use 25,000-50,000 U/kg/d IV divided qid; for severe disease use 250,000-400,000 U/kg/d IV in 4-6 divided doses >12 years: Administer as in adults |
| Contraindications | Documented hypersensitivity |
| Interactions | Effects are increased by coadministration with probenecid and decreased by coadministration with tetracyclines and other bacteriostatic antibiotics |
| Pregnancy | B - Usually safe but benefits must outweigh the risks. |
| Precautions | Caution in impaired renal function and newborns; rash; anaphylaxis; opportunistic infections with prolonged use; electrolyte imbalances with high doses (above 10 million U/d) if not administered slowly, frequently check electrolytes, renal function, and hematopoietic function (risk of positive Coombs' hemolytic anemia); black hairy tongue; Warner Chillcott's penicillin VK powder contains aspartame (if patient has PKU) |
| Drug Name | Penicillin VK (Beepen-VK, Betapen-VK, Pen-Vee K, Robicillin VK, Veetids) -- Interferes with synthesis of cell wall mucopeptide during active multiplication, resulting in bactericidal activity against susceptible microorganisms. Has better GI absorption than penicillin G |
|---|---|
| Adult Dose | 2-4 g/d PO in 4-6 divided doses (best if 1 h before or 2 h after meals) for 6-12 mo |
| Pediatric Dose | <1> >1 month: 15-62.5 mg/kg/d PO in 3-6 divided doses for 6-12 mo; not to exceed adult doses |
| Contraindications | Documented hypersensitivity |
| Interactions | Probenecid may increase effectiveness by decreasing clearance; tetracyclines are bacteriostatic, causing a decrease in the effectiveness of penicillins when administered concurrently |
| Pregnancy | C - Safety for use during pregnancy has not been established. |
| Precautions | Caution in renal impairment |
RSS Feed (xml)
