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Atypical mycobacteria

 

CHARACTER

TYPICAL

ATYPICAL

Staining reaction

Acid & alcohol fast

Acid & alcohol fast

Rate of growth

Slow 2-3 weeks

Some rapid growers (M. chelonei, M. fortuitum)

Growth within 1 wk

Temperature

37 degree

25-37°C

some grow at 44°C (M. xenopi, M. phlei, M. smegmatis)

Pigment

Buff

Some produce bright yellow/ orange pigment

Sensitivity to primary ATT

+

Usually resistant

Guinea pig inoculation

Pathogenic

Usually non pathogenic

Niacin

+

-

Neutral red

+

-

Aryl sulfatase

-

+

Catalase

-/ weak positive

+

 

G. Significance of atypical mycobacteria

  1. May cause a low grade tuberculin reaction
  2. May influence protective response to BCG
  3. False positive smears due to tap water lab contaminants
  4. Inverse relation with incidence of TB
  1. Classification of Atypical Mycobacteria
 
 

Runyon group

Name

Species

I

Photochromogens

M kansasii

M simiae

M marinum

II

Scotochromogen

M scrofulaceum

M gordonae

M szulgai

III

Non-photochromogens

M avium

M intracellulare

M xenopi

M ulcerans

M malmoense

IV

Rapid growers

M chelonei

M fortuitum


2. Diseases caused by Atypical Mycobacteria

Disease

Causative agent

Lymphadenopathy

M scrofulaceum

M avium Intracellulare

M szulgai

Pulmonary disease

M avium intracellulare

M kansasii

M xenopi, M simiae

Skin lesions

Buruli ulcer

Swimming pool granuloma/ fish tank granuloma

Post-injection abscesses

 

M ulcerans

 

M marinum

 

M chelonei, M fortuitum

Disseminated disease

AIDS related

Non-AIDS related

 

M avium intracellulare

 

M avium intracellulare, M chelonei





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