Nocardiaceae (Murray 3rd Ed pp 313)

The most important genus out of this species is Nocardia. Norcardia is an aerobic bacillus, gram-positive; cell wall contains mycolic acid, catalase +ve, use carbohydrates oxidatively, can grow on non-selective laboratory media, and acid fast. They form branched filaments in tissues, and culture. One way of distinguishing these from Actinomyces is the acid fastness.

Disease

Bronchopulmonary disease, develops slowly, (high predilection to spread to CNS via blood) develops after colonisation of oropharynx by inhaling spores into lower airways. Suppurative lesions occur when organism is traumatically introduced into the subcutaneous tissue. Disease characterised by necrosis, abscess formation. Examples of diseases: madura foot, mycetoma (Fig 39-3 Murray), chronic pneumonia, abscess of lungs, brain etc.

Diagnosis (Murray 3^rd Ed pp 315)

Specimens collected is dependent on clinical presentation of patient. If patient ≫ bronchopulmonary disease, take multiple sputum specimens due to slow growing nature of bacteria + contamination by commensal bacteria. Cutaneous abscess material easily recovered. Norcardia stains poorly with gram stains, and are partially acid fast. Usually no sulphur granules present, unless cutaneous involvement present. Morphology of colonies: white, wrinkled, soil smell. Incubation is at least 1 week.

Treatment (Murray 3^rd Ed pp 316)

Sulphonamides + streptomycin or tetracycline. Prognosis is poor for immunocompromised patients with disseminated disease.

Category: Microbiology Notes