Atypical mycobacteria & other zoonoses

Topic Completed: 1 September 2011

Minor changes: 11 October 2021

Copyright: 2003-2021,, Inc.

PubMed search: atypical [title] OR nontuberculous [title] mycobacteria lung

Elliot Weisenberg, M.D.
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Cite this page: Weisenberg E. Atypical mycobacteria & other zoonoses. website. Accessed October 28th, 2021.
Clinical features
  • Mycobacteria are present in soil and dust; are associated with domestic animals
  • Associated with immunosuppression (including AIDS patients with low CD4), chronic obstructive lung disease, prior TB, pneumoconiosis, bronchiectasis, bullous emphysema, lung carcinoma (Chest 2008;133:243)
  • Rarely immunocompetent patients, especially elderly females with right middle lobe involvement, cough and fatigue (Lady Windermere syndrome) (Chest 1992;101:1605)
  • AIDS patients have severe infection resembling tuberculosis with impaired T cell immunity; pulmonary involvement is part of disseminated disease
  • Different organisms vary in virulence
  • Radiographs show tree in bud opacifications
  • PCR or culture required for diagnosis
  • Mycobacterium avium complex (MAC) is most common; also M. kansasii, marinum, gordonae, scrofulaceum, xenopi, fortuitum, chelonei, abscessus (Emerg Infect Dis 2011;17:343)
  • Zoonoses are diseases and infections naturally transmitted between people and vertebrate animals (WHO: Zoonotic disease: Emerging Public Health Threats in the Region [Accessed 18 August 2021])
  • 3 classes:
    1. Endemic zoonoses which are present in many places and affect many people and animals
    2. Epidemic zoonoses which are sporadic
    3. Emerging and re-emerging zoonoses which are newly appearing in a population or have existed previously but are rapidly increasing in incidence
  • Zoonotic infection originally identified in lungs of foals; also cattle, swine, sheep, deer, goats, dogs, cats, other species
  • Worldwide distribution in water and soil, especially near feces of herbivores
  • Infection by inhalation or ingestion
  • Resides primarily within lung macrophages of infected patients, also some alveolar cells (Microbes Infect 2011;13:438)
  • R. equi is most common human pathogen of the Rhodococci
  • Generally occurs in AIDS patients (may cause malakoplakia) (Clin Infect Dis 1999;28:1334)
    • Also other immunodeficient patients; very rarely in immunocompetent
  • Incidence decreasing, likely due to HAART therapy and azithromycin prophylaxis
  • Rhodo since salmon pink pigment in culture
  • Treated with antibiotics but mortality is 50% in AIDS patients, 20% in other immunocompromised and 10% in immunocompetent
    Case reports
    Gross images

    Images hosted on other servers:
    Rhodococcus: pulmonary mass post renal transplant

    Rhodococcus: pulmonary mass post renal transplant

    Microscopic (histologic) description
    • Marked intraalveolar and parenchymal infiltration by foamy histiocytes or proteinaceous reaction, generally without tissue destruction, lymphoid infiltrates or granulomas
    • In AIDS patients, may see histiocytes packed with microorganisms without significant inflammatory response
    • Hantavirus: interstitial pneumonitis with mononuclear infiltrate, edema, focal hyaline membranes, pleura effusions; atypical lymphocytes in pulmonary vasculature may mimic lymphoma
    • Rhodococcus: epithelioid macrophages containing gram positive, partially acid fast coccobacilli that resemble mycobacteria; may produce malakoplakia
    Microscopic (histologic) images

    Images hosted on other servers:
    Mycobacterium avium complex - granulomatous inflammation Mycobacterium avium complex - granulomatous inflammation Mycobacterium avium complex - granulomatous inflammation Mycobacterium avium complex - granulomatous inflammation

    Mycobacterium avium complex: granulomatous inflammation

    Mycobacterium avium complex - granulomatous inflammation

    Granulomatous pneumonia from infection

    Mycobacterium avium complex - Ziehl Neelsen (acid fast) stain (right: lymph node)

    Ziehl-Neelsen acid fast stain

    Various images Various images


    Positive stains
    • Acid fast stains large numbers of intracellular bacteria; bacilli are longer (20 microns), more coarsely beaded and more bent than M. tuberculosis bacilli
    • PAS positive
    Electron microscopy images

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    Transmission electron<br>micrograph of<br>Sin Nombre hantavirus

    Transmission electron
    micrograph of
    Sin Nombre hantavirus

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