Atypical Mycobacterial Infection
Definition
An infection caused by a species of Mycobacterium other than tuberculosis that is often resistant to anti-tuberculous drugs.

Alternative Names
Mycobacteria other than tuberculosis (MOTT); Atypical Mycobacterial disease causes, incidence and risk factors.

Atypical Mycobacterial infection can cause infections such as abscesses, septic arthritis and osteomyelitis (bone infection), it can infect the lungs, lymph glands, skin or soft tissues.

Several species of Mycobacterium cause different infections. Mycobacterium avium intracellulare frequently affects AIDS patients. Mycobacterium marinum and M. ulcerans cause skin infections. M. marinum is responsible for swimming pool granuloma. M. avium-intracellulare and M. kansasii cause lung disease. M. scrofulaceum is a common cause of painless cervical lymphadenitis in children aged 1-5 years.

A typical Mycobacterial infections occur in approximately 3 out of 10,000 people annually but the incidence is increasing, as the immuno-compromised population grows due to the AIDS epidemic and the advent of chemotherapy. Populations at risk include individuals with pre-existing lung diseases and immuno-compromised persons.

Symptoms

	Fever
	Weight loss
	Enlarged lymph glands
	Diarrhea
	Excessive Night Sweats
	Fatigue
	General discomfort, uneasiness or ill feeling (malaise)

Laboratory Diagnosis

(A)	Bactec TB culture system for identification of MOTT: The following specimens may be checked

	Blood		Sputum
	Lymph node biopsies and aspirates		Bone marrow
	Body fluids		Stool

First the Mycobacteria is grown in the BACTEC 12B vials. The growth is monitored by BACTEC TB system. When optimum growth is reached (i.e. GI of 50-100), then the NAP test is put to differentiate between M. tuberculosis complex and MOTT bacilli.

Principle of the Test
NAP (p-nitro-a-acetylamino-B-hydroxy-propiophenone) an intermediate compound in the synthesis of Chloramphenicol, inhibits Mycobacteria belonging to the Tuberculosis complex, (M.tuberculosis, M.bovis, M.africanum and M.microti) almost completely, while other Mycobacteria show either slight or no inhibition. When Mycobacteria growth is inhibited in the presence of NAP, the evolution of 14CO2 is also inhibited, as indicated either by no increase or a decrease in the Growth Index. This effect on the GI is used as a tool for identification.
The results are available within 2-6 days after putting up the test.

(B)	Molecular method for identification of MOTT.

Recently developed molecular methods, such as DNA probe test and PCR can also be used to differentiate between MTB complex and MOTT.

Treatment
Treatment of the infection depends upon the sensitivity of the infecting organism to specific antibiotics. As many as 4-6 drugs may be used to treat some infections and treatment may require 6 months to 2 years. Certain lymph node infections and skin lesions can be surgically removed. Treatment in immuno-compromised patients may require even more extended periods.

Prognosis
The outcome depends upon the severity of the infection, the resistance of the organism, the individual's immune status and, ultimately, the response to treatment.

Bibliography

	Pitchenik AE, and Fertel D. 1992. Tuberculosis and non tuberculosis mycobacterial disease. Med. Clin. Am 76: 121-171
	Rogall T, Wolters J, Flohr T, and Bottger EC. 1990. Towards a phylogeny and definition of species at the molecular level within the genus Mycobacterium.Int. J. Syst. Bacteriol 40: 323-330