1. Non-tuberculous mycobacteria
Dr. Pendru Raghunath Reddy

2. Mycobacteria other than mammalian tubercle bacilli,
which may occasionally cause human disease are called
‘non-tuberculous mycobacteria’
Other names include atypical mycobacteria, anonymous,
unclassified Mycobacteria and Mycobacteria other than
M. tuberculosis (MOTT)

3. Runyoun classification
NTM have been categorized into four groups by Runyoun
(1959) based on pigment production and the growth rate
1. Photochromogenes
2. Scotochromogens
3. Non-photochromogens
4. Rapid growers

4. Runyon
Group
Number
Group Name
Description
I
Photochromogens
Colonies of NTM that develop pigment following
exposure to light after being grown in the dark and
take more than 7 days to appear on solid media
II
Scotochromogens
Colonies of NTM that develop pigment in the dark
or light and take more than 7 days to appear
on solid media
III
Nonphotochromogens
Colonies of NTM that are nonpigmented regardless
of whether they are grown in the dark or light
and take more than 7 days to appear on solid
media
IV
Rapid-growers
Colonies of NTM that appear on solid media in less
than 7 days

5. They are not usually transmitted from person to person
Source of infection is water, soil, food and animals
Human infection with NTM is common in some areas,
disease is rare
Exhibits dysgonic growth on LJ medium
Niacin and nitrate reduction tests are negative
Not able to cause progressive disease in guniea pigs

6. Photochromogens
The important species in this group are M. kansasii,
M. marinum and M. simiae
M. kansasii
M. kansasii causes chronic pulmonary disease resembling
tuberculosis
It may also occasionally cause infections of the cervical
lymphnodes, penetrating wound infections and
granulomatous synovitis
It can produce generalized infection in HIV patients

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8. Mycobacterium marinum
Causes a warty skin lesion known as swimming pool or
fish tank granuloma
Closely resembles M. kansasii but can be differentiated by
its poor growth at 370C, negative nitratase, and positive
pyrazinamide hydrolase

9. Fish tank granuloma

10. Scotochromogens
These strains form pigmented colonies (yellow-orange-red)
even in the dark
They are widely distributed in the environment and
sometimes contaminate cultures of tubercle bacilli

11. Important species in this group:
M. scrofulaceum may cause scrofula (cervical adenitis) in
children
M. gordonae often found in tap water is a common
contaminant in clinical specimens and a rare cause of
pulmonary disease
M. szulgai, an uncommon cause of pulmonary disease and
bursitis
It is a scotochromogen when incubated at 370C but a
photochromogen at 250C

12. Scrofula (cervical adenitis)

13. Non-photochromogens
Medically important species in this group are M. avium,
M. intracellulare, M. xenopi and M. ulcerans
M. avium
Which causes natural tuberculosis in birds and
lymphadenopathy in pigs, is one of the most common
opportunistic human pathogens
M. intracellulare
Is commonly known as Battey bacillus

14. M. avium and M. intracellulare are so similar that that they
have been considered as one group, the M. avium complex
(MAC)
MAC complex cause lymphadenopathy, pulmonary lesions
or disseminated disease, particulary in AIDS patients
M. xenopi, originally isolated from toads, may occasionally
cause chronic lung disease in human beings
M. ulcerans cause buruli ulcer

15. Rapid growers
This is a heterogeneous group of mycobacteria capable of
rapid growth, colonies appearing within 7 days of incubation
at 370C or 250C
Within the group, photochromogenic, scotochromogenic,
and non-chromogenic species occur
Most of these are purely are environmental saprophytes

16. The medically important species are M. fortuitum and
M. chelonae
M. fortuitum and M. chelonae occasionally cause pulmonary
or disseminated disease but are principally responsible for
postinjection abscesses and wound infections
Outbreaks of abscesses following injections of vaccines
contaminated by these mycobacteria have been reported

17. Lesions produced by NTM
1. Localized lymphadenitis
2. Skin lesions (Postinjection abscesses,
swimming pool granuloma and buruli ulcer)
3. Tuberculosis-like pulmonary lesions
4. Disseminated disease

18. Swimming pool granuloma
It is caused by M. marinum and is also known as fish tank
granuloma
M. marinum occurs as a saprophyte in fresh or salt water
Human infection originates from contaminated swimming
pools or fish tanks
The bacilli enter scratches and abrasions and cause warty
lesions similar to those seen in skin tuberculosis

19. The lesion, beginning as a papule and break down to form
an indolent ulcer
The disease is usually self-limiting although chemotherapy
with minocycline, cotrimoxazole or rifampicin with
ethambutol hastens its resolution

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21. Buruli ulcer
This disease is caused by M. ulcerans
The name is derived from the Buruli district of Uganda where a
large outbreak was extensively investigated
Ulcers are usually seen on the legs or arms and are believed to
follow infection through minor injuries
After an incubation period of a few weeks, indurated nodules
appear, which break down forming indolent ulcers which slowly
extend under the skin
When the immunoreactive phase sets in ulcers heal with
disfiguring scars

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