Mycobacterium Tuberculosis Morphology

Mycobacterium Tuberculosis Morphology


Mycobacterium Tuberculosis Morphology 

  • Mycobacterium tuberculosis is a slender, straight or slightly curved shape bacillus associated with rounded ends.
  • M. Tuberculosis is an aerobic, noncapsulated, non motile and non sporing bacteria.
  • Measurement – 1 – 4 um * 0.2 – 0.8 um in size.
  • It is found in pair or small clumps.
  • Ziehl neelsen staining technique is required to study the M. Tuberculosis morphology.
  • It is a gram positive Bacteria.


Cultural characteristics of Mycobacterium Tuberculosis

  • M. Tuberculosis is an aerobie in nature that grows slowly within 14 – 15 hours.
  • The organism grows at 37° C temperature with PH between 6.4 to 7.
  • The colonies appear within 2 weeks (sometimes within 6 – 8 weeks).
  • LJ medium (Low enstein Jensen) is commonly useful, that consist of asparagine, mineral salt eggs and glycerol.
  • Bacilli are grown as a surface pellicle in the liquid media.


Biochemical reaction mycobacterium tuberculosis

  • Nitrate reduction test and niacin test are the biochemical tests that are positive in the mycobacterium tuberculosis.


mycobacterium tuberculosis Resistance  

  • M. Tuberculosis survives in sputum for 20 – 30 hrs and in dust for several months.
  • It is destroyed at 60° C temperature for 20 minutes.



  • Tuberculosis disease involved pulmonary and extrapulmonary lungs.
  • M. Tuberculosis occurs due to inhalation of infected droplets, coughs or sneezes.
  • Bovine tuberculosis is developed due to infected cow milk.


Tuberculin skin test

  • It is a delayed and types 4th hypersensitivity reaction.
  • Resources – old tuberculin and purified protein derivative (PPD).
  • Old tuberculin described by Robert Koch is a crude product.
  • Methods – 0.1 ml of PPD is injected internally at the flexor aspect of the forearm.
  • Mark the inject site.
  • Result – Result are examined after 48 – 72 hours of PPD injected.
  • If Erythema diameter is 10 mm or more that indicates the positive tuberculin test.


Laboratory diagnosis of mycobacterium tuberculosis

    1. Specimen collection
  • Collect sputum for pulmonary tuberculosis.
  • Collect CSF for meningitis tuberculosis.
  • Collect morning urine for renal tuberculosis.
  • Biopsy of tissue is required for tissue tuberculosis.
  • For joint and bone tuberculosis, aspirate the fluid.


    1. Direct Microscopy
  • The specimen is stained by ziehl neelsen technique.
  • The acid fast Bacilli is appeased as a bright red Bacilli against a blue background.
  • Purulent part of the sputum is useful to prepare a smear.
  • The prepared smear is to be examined under fluorescent Microscopy.
  • Microscopy provides the only presumptive evidence of TB infection.


    1. mycobacterium tuberculosis Culture
  • It is a very sensitive method to determine the tubercle Bacilli.
  • Generally, the tubercle Bacilli grows in 2 to 8 weeks.
  • In the positive culture – calories appear on the culture medium, smear is made from the isolated colonies or stained with ziehl – neelsen technique.


    1. mycobacterium tuberculosis Serology 
  • The method used to detect the mycobacterium antibiotics in the patient serum.
  • Serology include following test
  1. ELISA
  2. RIA
  3. Latex agglutination assay.


    1. Molecular methods 
  • PCR (polymerase chain reaction) is a rapid diagnostic method of Tuberculosis.
  • PCR test is based on the DNA amplification that detects the M. Tuberculosis directly in the clinical specimen.


Treatment of mycobacterium tuberculosis:-

  • Common antitubercular drugs are – isoniazid, rifampicin, streptomycin, pyrazinamide, ethambutol etc.
  • BCG vaccine – proposed by the calmette and guerin in 1921.
  • BCG is – Bacilli calmette guerin.
  • BCG dose – 0.1 ml at 1 month of birth and 0.05 ml at the birth.
  • The BCG vaccine is around 80% effective to protect against tuberculosis.

Read  Other Articles Related to Tuberculosis……..

🔴what is tuberculosis? Symptom Cause and Treatment

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🔴 MOST Common Cause, Type, Symptom Of Any Disease 

Reference – Textbook of microbiology 5th edition by Dr. C.P. Baveja.

Page no. – 330 – 340.

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