What is Nocardiosis?

From the Guidelines

Nocardiosis is a rare bacterial infection caused by Nocardia species, primarily affecting the lungs, skin, and central nervous system, and is most common in immunocompromised individuals. According to the practice guidelines for the diagnosis and management of skin and soft tissue infections updated by the Infectious Diseases Society of America in 2014 1, Nocardia infections usually represent metastatic foci of infection that have originated from a primary pulmonary source. The dermatologic manifestations are usually limited to subcutaneous nodules or abscesses and panniculitis.

Key Characteristics of Nocardiosis

• Cutaneous Nocardia infections are often associated with Nocardia farcinica, Nocardia brasiliensis, and other Nocardia species
• Soft tissue abscesses are frequently painless and are described as being cold to the touch
• The incidence of local and disseminated Nocardia infections has decreased with the routine use of SMX-TMP prophylaxis for patients who experience prolonged periods of cellular immune deficiency

Treatment of Nocardiosis

• SMX-TMP remains the treatment of choice, but other sulfa antibiotics (eg, sulfadiazine and sulfasoxazole), amikacin, imipenem, meropenem, third-generation cephalosporins (ceftriaxone and cefotaxime), minocycline, extended-spectrum fluoroquinolones (eg, moxifloxacin), linezolid, and dapsone are effective in vitro and in animal models
• Combination therapy with other agents should be considered in patients with severe infections or profound and lasting immunodeficiency
• Prolonged therapy is important, and the duration of treatment (6–24 months) should take into account the presence of disseminated disease and the extent of the patient’s underlying immunosuppression
• Surgical debridement is recommended for necrotic nodules or large subcutaneous abscesses, as stated in the guidelines 1

From the Research

Definition and Causes of Nocardiosis

• Nocardiosis is a rare bacterial infection caused by Nocardia spp. 2, 3, 4, 5
• It is an opportunistic disease that affects mainly patients with deficient cell-mediated immunity, such as those with acquired immunodeficiency syndrome (AIDS) or transplant recipients 4
• The disease can be acquired through inhalation of the bacteria or through direct inoculation of the organism through professional exposure 4

Clinical Manifestations and Diagnosis

• The clinical manifestations of nocardiosis are nonspecific and can include fever, cough, and skin lesions 3, 5
• The diagnosis can be challenging and requires a high index of clinical suspicion 4
• Gram stain, modified acid-fast stain, and cultures are the standard diagnostic tools, while novel molecular techniques have changed the taxonomy of these organisms and facilitated their identification 4

Treatment and Outcome

• Treatment of nocardiosis is usually prolonged and requires antibiotic therapy, with sulfonamides in combination with other antibiotics being the treatment of choice 2, 3, 4
• Linezolid is a useful alternative therapeutic agent due to its oral availability and activity against most of the isolates studied 4
• The disease has a marked tendency to recur and a high morbidity and mortality rate in immunosuppressed patients 4
• Early diagnosis and prompt aggressive interventions are important to improve the outcome of this disease 5

Epidemiology and Risk Factors

• Nocardiosis is a rare disease, but its incidence is increasing 2
• The disease is more common in immunosuppressed patients, such as those with AIDS or transplant recipients 4
• Other risk factors include age, gender, and underlying medical conditions 2, 5
• The most common species of Nocardia isolated are N. cyriacigeorgica, N. nova, and N. farcinica 2, 6