Pathogenesis and Immunity - Nocardia

Pathogenesis and Immunity

Nocardia species are opportunistic pathogens. Nocardia causessuppurative necrosis with the formation of abscesses at the site of infection. These species cause following infections:

·           Cutaneous nocardiosis arises from the local trauma intothe surface of the skin, which facilitates entry of the organ-ism into subcutaneous tissues.

·           Pleuropulmonary disease occurs most commonlydue to inhalation of infectious aerosols. This condi-tion is most commonly seen in immunocompromised individuals, including the patients with AIDS (acquired immunodeficiency syndome) and the patients receiv-ing immunosuppressive therapy. The condition is also common in patients with chronic pulmonary disease such as emphysema, bronchitis, bronchiectasis, etc. The infection begins after colonization of the oropharynx by inhalation of infective aerosols. This is followed by aspira-tion of pleural secretions into the lower respiratory tract. Disseminated infection is usually secondary to pleuropul-monary infection that has occurred earlier in the lungs. The disseminated infection occurs most commonly in individuals receiving immunosuppressive therapy or with underlying immunocompromised diseases. The patients who have received organ, bone marrow, or stem cell transplantation and patients with cirrhosis, lymphoretic-ular malignancies, and SLE (systemic lupus erythemato-sus) are more susceptible to infection.

N. asteroides is the most important species causing approxi-mately 90% of human infections.