Microbiology & parasitology


Mycobacteria non TB

Topic Completed: 1 February 2014

Minor changes: 18 October 2021

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PubMed Search: Mycobacteria[title] colon

Lili Lee, M.D.
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Cite this page: Lee L. Mycobacteria non TB. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/colonMAI.html. Accessed January 21st, 2022.
Definition / general
  • Associated with HIV infection
  • Recommended to perform acid-fast stain on all mucosal biopsies in HIV+ patients
  • If present in gut, is usually disseminated, with positive stool and blood cultures
  • Mycobacteria other than TB (MOTT)
  • Nontuberculous mycobacteria (NTM)
  • Of the Mycobacteria other than TB (MOTT), Mycobacterium avium-intracellulare complex (MAC) is the most commonly isolated mycobacteria
  • Often associated with HIV infection, commonly infects immunocompromised and elderly patients
  • May be due to contaminated endoscope (Kekkaku 1995;70:629)
  • Ileocecal area is most commonly involved (90%) similar to Mycobacterium tuberculosis infection
Clinical features
  • Nonspecific symptoms of fever, night sweats, weight loss, fatigue, diarrhea, abdominal pain
  • AFB smear, blood/sterile site culture, tissue biopsy
  • Multiplex PCR, DNA probes, DNA sequencing for specific NTM speciation
  • MAI complex:
    • No cording on Lowenstein-Jensen/Middlebrook broth
    • Nitro-α acetylamino β hydroxypropiophenone (NAP test) resistant (vs. Mycobacterium TB which is inhibited)
    • Para-nitrobenzoic acid (PNB test) resistant (J Lab Physicians 2010;2:89)
    • Non-chromogen
    • Slow grower (>7 days), and niacin inhibits growth
Radiology images

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Jejunal loops and extensive ymphadenopathy (MAI)

Case reports
  • Two or more antimycobacterial drugs (clarithromycin, ethambutol, rifampin, etc.)
Gross description
  • Diffuse mucosal fold thickening mimicking Whipple disease
Microscopic (histologic) description
  • Lamina propria expanded by a lymphohistiocytic infiltrate
  • Duodenal infection may resembles Whipple disease, but without fat vacuoles
Microscopic (histologic) images

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Colonic crypt and masses of histiocytes

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Histiocytes in lamina propria (PAS)

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Intracytoplasmatic short acid fast bacilli (Ziehl-Neelsen)

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H&E and AFB

Positive stains
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