Concise review for clinicians
Nocardiosis: Updates and Clinical Overview

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Abstract

Nocardia, a gram-positive bacillus with the microscopic appearance of branching hyphae, can produce considerable disease in the appropriate host. The taxonomy of Nocardia continues to evolve; more than 50 species have been described. Early recognition and effective therapy are imperative to achieve successful outcomes. Although nocardiosis typically occurs in patients with cell-mediated immunosuppressive conditions, infection may occasionally develop in immunocompetent patients as well. This review addresses the microbiology of Nocardia, risk factors for infection, clinical presentations, and management strategies.

Section snippets

Risk Factors for Infection

Nocardia usually is an “opportunistic pathogen,” with the majority of infections occurring in patients with immunosuppressive conditions. Up to one-third of patients with nocardiosis, however, are immunocompetent.5 Irrespective of a patient's immunologic status, the isolation of Nocardia from the respiratory tract or other body source should not be regarded as a contaminant or commensal organism. Patients with depressed cell-mediated immunity especially are at high risk for infection, including

Clinical Presentations

Pulmonary nocardiosis is the most common clinical presentation of infection because inhalation is the primary route of bacterial exposure. The onset of symptoms may be subacute to more chronic and can include productive or nonproductive cough, shortness of breath, chest pain, hemoptysis, fever, night sweats, weight loss, and progressive fatigue. The chest radiograph can be variable, displaying focal or multifocal disease with nodular and/or consolidation infiltrate as well as cavitary lesions.18

Treatment Considerations

General treatment recommendations for nocardiosis are hindered by the lack of prospective controlled trials. Optimal antimicrobial treatment regimens have not been firmly established. Nocardia displays variable in vitro antimicrobial susceptibility patterns, and management of nocardial infections must be individualized.26 The Clinical and Laboratory Standards Institute has published recommendations for antimicrobial susceptibility testing for Nocardia and other aerobic actinomycetes.27 Nocardia

Conclusion

Increases in the number of patients receiving immunosuppressive therapies for solid organ or hematopoietic stem cell transplants, hematologic and solid tissue cancers, and autoinflammatory conditions, ensure that Nocardia will remain a formidable pathogen. Although this organism is capable of producing serious and metastatic disease in the appropriate host, early recognition and initiation of appropriate treatment can lead to successful outcomes.

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