Microbiology & parasitology
Mycobacteria
Mycobacteria non TB
Author: Lili Lee, M.D.
Topic Completed: 1 February 2014
Minor changes: 18 October 2021
Copyright: 2003-2022, PathologyOutlines.com, Inc.
PubMed Search: Mycobacteria[title] colon
Table of Contents
Definition / general | Terminology | Epidemiology | Sites | Clinical features | Diagnosis | Laboratory | Radiology images | Case reports | Treatment | Gross description | Microscopic (histologic) description | Microscopic (histologic) images | Positive stains | Additional referencesCite 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
Terminology
- Mycobacteria other than TB (MOTT)
- Nontuberculous mycobacteria (NTM)
Epidemiology
- 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)
Sites
- 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
Diagnosis
- AFB smear, blood/sterile site culture, tissue biopsy
- Multiplex PCR, DNA probes, DNA sequencing for specific NTM speciation
Laboratory
- 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
Images hosted on other servers:
Jejunal loops and extensive ymphadenopathy (MAI)
Case reports
- 64 year old woman with previous mycobacterial infection and a colonic stricture (Postgrad Med J 2003;79:705)
- Patient receiving immunosuppressive therapy with severe gastrointestinal hemorrhage (Am J Gastroenterol 1999;94:232)
Treatment
- 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
Images hosted on other servers:
Colonic crypt and masses of histiocytes
Histiocytes in lamina propria (PAS)
Intracytoplasmatic short acid fast bacilli (Ziehl-Neelsen)
H&E and AFB
Positive stains
- Acid-fast stains, PAS (faintly positive bacillary forms)
