Nocardiosis

Basics

A rare infectious disease caused by Nocardia spp. which are primarily located in ground and water sources
No pathognomonic presentation
Nocardiosis can be acute, subacute, or chronic, and involves multiple systems:
- Pulmonary (>70% overall, 39% only lung)
- Disseminated: ≥2 sites (32% overall)
- Cutaneous (~8%)
- CNS (20% overall, 44% of disseminated, 9% brain only)
Patients are typically immunocompromised or have chronic pulmonary or systemic disease.
Less commonly, Nocardia can infect the eye, heart, bone, soft tissues, and any other organ system.

Nocardia spp. are aerobic gram-positive branching rods found worldwide in soil, decaying plants, fresh and salt water.
>80 species, >30 of which cause human disease.
Nocardia asteroides complex causes the majority of symptomatic infections and includes Nocardia abscessus, Nocardia cyriacigeorgica, Nocardia farcinica, and Nocardia nova.
Nocardia enters through inhalation (e.g., contaminated dust), traumatic skin inoculation, or ingestion.
Nocardiosis of the skin has four patterns: primary cutaneous, lymphocutaneous, cutaneous secondary to disseminated spread, and mycetoma.
Pulmonary, CNS, and other organ system infection with Nocardia is typically suppurative, often leading to abscess formation.
Incubation period: days to weeks
Pathologic Nocardia spp. have several intrinsic means of overcoming host immune responses.

Most cases occur in immunocompromised hosts, particularly those with impaired cell-mediated immunity. Other chronic diseases (e.g., diabetes mellitus [DM], COPD) may predispose individuals to nocardiosis.
Farm workers and other immunocompetent individuals may develop pulmonary, cutaneous, and disseminated disease if sufficiently exposed.
Nocardiosis can be severe and fatal in immunocompromised patients; immunocompetent individuals rarely develop severe disease.
Immunocompromised children are also at risk.

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