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Nocardiosis is an acute, subacute, or chronic infectious disease that occurs in cutaneous, pulmonary, and disseminated forms. Primary cutaneous nocardiosis manifests as cutaneous infection (cellulitis or abscess), lymphocutaneous infection (sporotrichoid nocardiosis), or subcutaneous infection (actinomycetoma). Pleuropulmonary nocardiosis manifests as an acute, subacute, or chronic pneumonitis, usually in immunocompromised hosts, although isolated cases have been reported in immunocompetent hosts. Disseminated nocardiosis may involve any organ; lesions in the brain or meninges are most common.

Members of the genus Nocardia are aerobic actinomycetes that are ubiquitous saprophytes in soil, decaying organic matter, and fresh and salt water. Over 100 species of the genus Nocardia have been identified, more than half of which have been described during the last decade.

The taxonomy has been challenging and likely remains in evolution. [1, 2] Most human infections are due to members of the formerly called Nocardia asteroides complex. N asteroides complex was later separated into Nocardia abscessus, Nocardia brevicatena-paucivorans complex , Nocardia nova complex, Nocardia transvalensis complex, Nocardia farcinica, Nocardia asteroides sensu stricto, and Nocardia cyriacigeorgica; however, use of the term ” N asteroides complex” is currently outdated because of the heterogenous group of organisms it includes. Nocardia species also cause infections in animals, including bovine mastitis and sporotrichoid nocardiosis in horses.

When observed microscopically, either in Gram-stained smears of clinical specimens or cultures or on histopathology in tissues, Nocardia organisms are branching, beaded, filamentous, gram-positive bacteria with a characteristic morphology to a trained observer. See the image below.

Nocardia are typically weakly acid-fast after traditional staining and positive on modified acid-fast staining, but this is not invariable.

The cutaneous, lymphocutaneous, and subcutaneous forms of nocardiosis arise from local traumatic inoculation. These infections are not necessarily associated with immunocompromised host states, but dissemination from these sites of inoculation is more likely in immunocompromised hosts, particularly those with impaired cell-mediated immunity. Pleuropulmonary nocardiosis presumably arises from inhalation exposure. Disseminated nocardiosis results from hematogenous dissemination, usually from a pulmonary focus. Most persons with disseminated nocardiosis have underlying immunocompromising disease or are receiving immunosuppressive therapy.

Nocardiosis produces suppurative necrosis with frequent abscess formation at sites of infection. See the image below.

Disease manifestations of nocardiosis are determined by strain characteristics, inoculation site, tissue tropism, ability to survive initial neutrophilic leukocyte phagocytic attack, and the nature of the immune response. T-cell–mediated immunity is the principal protective immune response to nocardiosis. [3] Therefore, nocardiosis is most problematic in individuals with impaired T-cell–mediated immunity. [2]

United States

The estimated incidence of nocardiosis in the United States is 500-1000 cases per year. [4]

Clusters of nocardiosis have been described in hospitalized patients, related to contaminated fomites from construction or contaminated hands of staff.


No reliable estimates on the international frequency of nocardiosis are available.

Nocardiosis has a variable prognosis, depending on the site of infection, extent of infection, and underlying host factors. [5]

Cure rates with appropriate therapy are approximately 100% in skin and soft-tissue infections.

Ninety percent of pleuropulmonary infections can be cured with appropriate therapy.

The cure rate in disseminated nocardiosis falls to 63%, while only half of patients with brain abscess can be cured with therapy. [6]

Nocardiosis has no apparent racial predilection.

Nocardiosis is more common in males than in females, with a male-to-female ratio of 3:1. This difference may be related to exposure frequency rather than a gender difference in susceptibility.

All ages are susceptible to nocardiosis. The mean age at diagnosis is in the fourth decade of life.

Patients with nocardiosis must be educated about the need for protracted antimicrobial therapy.

Patients with nocardiosis should be informed of the potential adverse effects of protracted antimicrobial therapy and which circumstances require reporting to their physician promptly.

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Lavalard E, Guillard T, Baumard S, Grillon A, Brasme L, Rodríguez-Nava V, et al. Brain abscess due to Nocardia cyriacigeorgica simulating an ischemic stroke. Ann Biol Clin (Paris). 2013 Jun 1. 71(3):345-348. [Medline].

Boiron P, Locci R, Goodfellow M, et al. Nocardia, nocardiosis and mycetoma. Med Mycol. 1998. 36 Suppl 1:26-37. [Medline].

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Hui CH, Au VW, Rowland K, Slavotinek JP, Gordon DL. Pulmonary nocardiosis re-visited: experience of 35 patients at diagnosis. Respir Med. 2003 Jun. 97(6):709-17. [Medline].

Kilincer C, Hamamcioglu MK, Simsek O, et al. Nocardial brain abscess: review of clinical management. J Clin Neurosci. 2006 May. 13(4):481-5. [Medline].

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Matulionyte R, Rohner P, Uckay I, et al. Secular trends of nocardia infection over 15 years in a tertiary care hospital. J Clin Pathol. 2004 Aug. 57(8):807-12. [Medline].

Pintado V, Gomez-Mampaso E, Cobo J, et al. Nocardial infection in patients infected with the human immunodeficiency virus. Clin Microbiol Infect. 2003 Jul. 9(7):716-20. [Medline].

Saubolle MA, Sussland D. Nocardiosis: review of clinical and laboratory experience. J Clin Microbiol. 2003 Oct. 41(10):4497-501. [Medline].

Pilsczek FH, Augenbraun M. Mycetoma fungal infection: multiple organisms as colonizers or pathogens?. Rev Soc Bras Med Trop. 2007 Jul-Aug. 40(4):463-5. [Medline].

Martinez Tomas R, Menendez Villanueva R, Reyes Calzada S, et al. Pulmonary nocardiosis: risk factors and outcomes. Respirology. 2007 May. 12(3):394-400. [Medline].

Rosman Y, Grossman E, Keller N, Thaler M, Eviatar T, Hoffman C, et al. Nocardiosis: A 15-year experience in a tertiary medical center in Israel. Eur J Intern Med. 2013 May 29. [Medline].

Lerner PI. Nocardiosis. Clin Infect Dis. 1996 Jun. 22(6):891-903; quiz 904-5. [Medline].

Beaman BL, Beaman L. Nocardia species: host-parasite relationships. Clin Microbiol Rev. 1994 Apr. 7(2):213-64. [Medline]. [Full Text].

Peleg AY, Husain S, Qureshi ZA, et al. Risk factors, clinical characteristics, and outcome of Nocardia infection in organ transplant recipients: a matched case-control study. Clin Infect Dis. 2007 May 15. 44(10):1307-14. [Medline].

Uhde KB, Pathak S, McCullum I Jr, et al. Antimicrobial-resistant nocardia isolates, United States, 1995-2004. Clin Infect Dis. 2010 Dec 15. 51(12):1445-8. [Medline].

Brown-Elliott BA, Biehle J, Conville PS, Cohen S, Saubolle M, Sussland D. Sulfonamide resistance in isolates of Nocardia spp. from a US multicenter survey. J Clin Microbiol. 2012 Mar. 50(3):670-2. [Medline].

Minero MV, Marin M, Cercenado E, Rabadan PM, Bouza E, Munoz P. Nocardiosis at the turn of the century. Medicine (Baltimore). 2009 Jul. 88(4):250-61. [Medline].

George Kurdgelashvili, MD Clinical Associate Professor of Medicine, Department of Medicine, University of Oklahoma College of Medicine; Assistant Chief of Medical Service, Director of Diagnostic Center Clinic, Chair of Infection Prevention and Control Committee, Attending Physician, Infectious Diseases Section, Oklahoma City Veterans Affairs Medical Center

George Kurdgelashvili, MD is a member of the following medical societies: Infectious Diseases Society of America, HIV Medicine Association, Veterans Affairs Society of Practitioners in Infectious Diseases

Disclosure: Nothing to disclose.

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

John W King, MD Professor of Medicine, Chief, Section of Infectious Diseases, Director, Viral Therapeutics Clinics for Hepatitis, Louisiana State University Health Sciences Center; Consultant in Infectious Diseases, Overton Brooks Veterans Affairs Medical Center

John W King, MD is a member of the following medical societies: American Association for the Advancement of Science, American College of Physicians, American Federation for Medical Research, Association of Subspecialty Professors, American Society for Microbiology, Infectious Diseases Society of America, Sigma Xi

Disclosure: Nothing to disclose.

Michael Stuart Bronze, MD David Ross Boyd Professor and Chairman, Department of Medicine, Stewart G Wolf Endowed Chair in Internal Medicine, Department of Medicine, University of Oklahoma Health Science Center; Master of the American College of Physicians; Fellow, Infectious Diseases Society of America; Fellow of the Royal College of Physicians, London

Michael Stuart Bronze, MD is a member of the following medical societies: Alpha Omega Alpha, American College of Physicians, American Medical Association, Association of Professors of Medicine, Infectious Diseases Society of America, Oklahoma State Medical Association, Southern Society for Clinical Investigation

Disclosure: Nothing to disclose.

Thomas J Marrie, MD Dean of Faculty of Medicine, Dalhousie University Faculty of Medicine, Canada

Thomas J Marrie, MD is a member of the following medical societies: Alpha Omega Alpha, American College of Physicians, American Society for Microbiology, Association of Medical Microbiology and Infectious Disease Canada, Royal College of Physicians and Surgeons of Canada

Disclosure: Nothing to disclose.


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