Actinomycosis
Actinomycosis is a chronic, slowly progressive suppurative infection caused by Actinomyces israelii, normal oral/GI/reproductive flora that becomes invasive after mucosal trauma. It classically produces cervicofacial, thoracic, abdominal, or pelvic disease with draining sinus tracts and sulfur granules, and is treated with prolonged high-dose penicillin.
- Topic reviewThe full article, organized the way the exam asks it.
- ABIM-format MCQsVignettes with an explanation for every wrong answer.
- Key factsThe numbers and thresholds worth memorizing, up front.
- AI tutorMedBrain answers the question you're stuck on.
What this article covers
- Overview
Chronic suppurative infection by normal flora gone invasive: actinomycosis is caused by Actinomyces israelii, an anaerobic, gram-positive, branching filamentous organism that is part of normal oral…
- Epidemiology
Uncommon but likely underdiagnosed: because the presentation mimics malignancy or chronic granulomatous disease and cultures require prolonged anaerobic incubation, many cases are diagnosed only…
- Risk factors
Dental and oral mucosal trauma: tooth extraction, dental caries, and poor dental hygiene are the leading antecedents for cervicofacial disease.
- Pathophysiology
Endogenous flora breaches a mucosal barrier: Actinomyces is not acquired from the environment; it is normal flora that gains access to deep tissue through trauma, extraction, aspiration, or bowel wall disruption.
- Clinical features
Cervicofacial disease (most common): a chronic, indurated, "woody" swelling of the jaw or neck (classically after dental extraction) that develops one or more chronically draining sinus tracts discharging pus containing sulfur granules.
- Differential diagnosis
Malignancy (squamous cell carcinoma, lymphoma, or a primary lung/abdominal tumor): most dangerous mimic given the mass-forming, tissue-plane-crossing behavior; distinguished by biopsy showing sulfur…
- Diagnosis
This is a microbiologic and histopathologic diagnosis confirmed by identifying Actinomyces in tissue or pus, established through the following ordered workup: the clinching finding is sulfur granules…
- Management
Start penicillin G as first-line therapy, dosed as 4000000 units IV every 4 hours (18-24 million units/day total): given as this divided schedule or as an equivalent continuous infusion, for 2 to 6…
- Complications
Extensive local tissue destruction and fistula formation: chronic untreated disease erodes through fascial planes, bone, and skin, producing disfiguring sinus tracts and fistulas to adjacent viscera (bowel, bladder).
- Prognosis
Excellent with adequate, prolonged antibiotic therapy: actinomycosis is a curable infection in a host with normal immunity when penicillin-based therapy is continued for the full recommended duration.
- Prevention
Maintain routine dental care (cleaning and caries management at least every 6-12 months) to limit the periodontal trauma that seeds cervicofacial disease.
Read the whole article
Subscribing to Internal Medicine opens every article, the full question bank and MedBrain, on the web, iPhone and Android.
Related articles
- Nocardiosis
Nocardiosis is an opportunistic infection caused by aerobic, weakly acid-fast, branching gram-positive Nocardia species acquired from soil by inhalation or direct inoculation, most often producing necrotizing pulmonary disease with a strong tendency to hematogenously seed the brain, diagnosed by modified acid-fast stain and prolonged culture, and treated with high-dose trimethoprim-sulfamethoxazole, escalated with amikacin and imipenem for disseminated or CNS disease.
- Pelvic inflammatory disease
Pelvic inflammatory disease is an ascending polymicrobial infection of the upper female genital tract, most often caused by Neisseria gonorrhoeae, Chlamydia trachomatis, or Mycoplasma genitalium, diagnosed clinically on uterine, adnexal, or cervical motion tenderness. Most women are treated as outpatients with a single dose of ceftriaxone plus 14 days of doxycycline, while parenteral cefotetan or cefoxitin plus doxycycline, or clindamycin plus gentamicin, is reserved for hospitalized patients, with tubo-ovarian abscess and infertility among the major complications of delayed treatment.
- Tuberculosis
Tuberculosis, caused by Mycobacterium tuberculosis, remains a leading global cause of infectious death and presents as latent infection, primary/secondary pulmonary disease, or extrapulmonary and disseminated (miliary) disease. Diagnosis rests on AFB smear, NAAT, and mycobacterial culture (the gold standard), and drug-susceptible active disease is treated with a four-drug regimen (isoniazid, rifampin, pyrazinamide, ethambutol) for 2 months followed by isoniazid plus rifampin for 4 to 7 months.
- Osteomyelitis
Osteomyelitis is bone infection from hematogenous seeding or contiguous spread, most often from Staphylococcus aureus, presenting as subacute pain with or without a draining sinus tract and confirmed by bone biopsy culture. Empiric antibiotics are withheld until biopsy in a stable patient, and treatment combines source control with 4 to 6 weeks of culture-directed antibiotics, extended to 6 weeks or indefinite suppression for hardware-associated or chronic disease.
- Blastomycosis
Blastomycosis is a dimorphic fungal infection acquired by inhaling Blastomyces dermatitidis conidia in the Mississippi and Ohio River valleys, presenting as primary pulmonary infection that can mimic lung cancer or disseminate to skin and bone, diagnosed by direct fungal stain confirmed with culture, antigen, or serology, and treated with itraconazole for mild to moderate disease or liposomal amphotericin B for severe, disseminated, or CNS disease.
- Histoplasmosis
Histoplasma capsulatum is an endemic dimorphic fungus, acquired by inhalation of conidia in the Mississippi and Ohio River valleys and other endemic regions, that most often causes asymptomatic or mild pulmonary infection but can disseminate in immunosuppressed hosts; diagnosis rests on the Histoplasma urinary antigen assay and treatment is itraconazole for mild to moderate disease or liposomal amphotericin B followed by itraconazole for severe or disseminated infection.
- Coccidioidomycosis
Coccidioidomycosis, or valley fever, is a dimorphic fungal infection acquired by inhaling Coccidioides arthroconidia in the southwestern United States, ranging from self-limited pneumonia to disseminated or meningeal disease, diagnosed by culture, histopathology, or serology and treated with fluconazole for symptomatic disease and lifelong fluconazole for meningitis.