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Chapter: Microbiology and Immunology: Bacteriology: Actinomycetes

Laboratory Diagnosis - Nocardia Infections

Laboratory diagnosis of nocardiosis depends on the demon-stration of Nocardia by microscopy and isolation by culture.

Laboratory Diagnosis

Laboratory diagnosis of nocardiosis depends on the demon-stration of Nocardia by microscopy and isolation by culture.

 Specimens

Nature of the clinical specimens depends on clinical presen-tation of nocardiosis. Sputum is a frequently used specimen. Other specimens include respiratory secretions, skin biopsies, or pus from the abscesses.

 Microscopy

Diagnosis is made by demonstration of branching actinomy-cotic filaments in pus or in multiple sputum specimens by microscopy. Smears from the specimen are stained by Gram or Ziehl–Neelsen method.


 Culture

Pus, sputum, and granules are cultured on nutrient agar, BHI agar, and Sabouraud’s agar and are incubated at 36°C for up to 3 weeks. Colonies on these media may appear as early as 7 days.

 Identification of bacteria

The colonies are identified on the basis of Gram-positive and weekly acid-fast positive filamentous bacilli and with other biochemical properties. All the species of the genus Nocardia(N. asteroides com-plex, N. brasiliensis, and N. otitidiscaviarumN. asteroides complex including N. asteroidesN. farcinica, and N. nova) are identified by using a battery of biochemical tests (Table 46-2).




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Microbiology and Immunology: Bacteriology: Actinomycetes : Laboratory Diagnosis - Nocardia Infections |


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