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.

Pathogenesis 

• 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.

• 2. 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.

• 3. 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.

• 4. 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.

• 5. 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

????Nosocomial infection

???? MOST Common Cause, Type, Symptom Of Any Disease 

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

Page no. – 330 – 340.