Mycobacterium Tuberculosis Question And Answers

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Mycobacterium Tuberculosis Long Essay

Question 1. Describe morphology, cultural characteristics, pathogenicity, and laboratory diagnosis of mycobacterium tuberculosis.
Answer:

Mycobacterium tuberculosis Morphology:

  • M. Tuberculosis is weakly gram-positive, strongly acid- fast bacilli.
  • They are non-sporing, non-capsulated and non-motile.
  • Shape-slender, straight or slightly curved bacilli with rounded ends.
  • Size : 1 – 4 0m * 0.2 – 0.8 0m.
  • Arrangement – singly, in pairs or in small clumps.

Mycobacterium tuberculosis Cultural characteristics:

  • M. Tuberculosis is an obligate aerobe.
  • It grows slowly at a temperature range of 30 – 40°C and pH – 6.4 – 7.0.

1. Lowenstein – Jensen media.

  • It consists of
    • Beaten eggs – Acts as a solidifying agent.
    • Asparagine.
    • Mineral salts.
    • Malachite green – Inhibits the growth of another organism.
    • Glycerol – Improves growth.
    • Colonies are dry, rough, buff-colored, raised with a wrinkled surface.

2. Liquid media.

  • Bacilli grow as a surface pellicle.
  • Virulent strains grow as serpentine cords.
  • Avirulent strains grow in a dispersed fashion.

Mycobacterium tuberculosis Pathogenicity:

  • Route of infection – inhalation, ingestion, and skin inoculation.
  • Tubercle is a characteristic lesion.
  • It is an avascular granuloma composed of a central zone containing giant cells with or without caseation necrosis surrounded by epitheloid cells and a peripheral zone of lymphocytes and fibroblasts.

Mycobacterium tuberculosis Types:

1. Exudative.

  • It is an acute inflammatory reaction with an accumulation of edema fluids, leucocytes, and monocytes.

2. Productive.

  • It is predominantly cellular and composed of tubercles.
  • Tuberculosis can also be classified as.

1. Primary infection.

  • Occurs in young children.
  • Leads to primary complex.
  • Consists of Gohn’s focus.
  • Hilar lymph nodes are involved.

Read And Learn More: Microbiology Question and Answers

2. Postprimaiy infection.

  • Occurs in adults.
  • It heals by resorption, fibrosis and occasionally

Lab Diagnosis of My-cobacterium Tuberculosis

1. Specimen collection

Mycobacterium Tuberculosis Specimen collection

2. Direct microscopy

  • Ziehl Neelsen staining shows acid-fast, bright red tubercle bacilli.

3. Culture.

  • Lowenstein – Jension media is used.

4. Animal inoculation.

  • 0.5 ml of the concentrated specimen is inoculated IM into the thigh of two healthy guinea pigs.
  • Animals are weighed before inoculation and then at weekly intervals.
  • Tested after 3-4 weeks.
  • Auto spy shows a caseous lesion.

5. Molecular method – Includes polymerase chain reaction.

6. Serological test – Includes.

  • ELSI test
  • Radioimmunoassay.
  • Latex agglutination assay.

Mycobacterium Tuberculosis Short Essays

Question 1. Mantoux test.
Answer:

It is routinely used method for tuberculin testing.

Mantoux test Method:

  • 0.1 ml of purified protein derivative, PPD containing 5 TU [tuberculin unit] is injected intradermally into the flexor aspect of the forearm.
  • It is given between layers of the skin.
  • The site is examined after 48 – 72 hours for induration.

Mantoux test Result:

Mycobacterium Mantoux test result

Mantoux test Significance:

Mycobacterium Mantoux test significance

Question 2. BCG vaccine.
Answer:

  • BCG vaccine was prepared by Calmette and Guerin.
  • It is a live attenuated and freeze-dried vaccine.

BCG vaccine Dose and Administration:

  • It is available as a fresh liquid vaccine or in the form of freeze-dried vaccine.
  • It is given intradermally in a dose of 0.1 ml soon after birth.

BCG vaccine Immune response:

  • Induces a self-limited infection with multiplication and dissemination of the bacillus in different organs and production of small tubercles.
  • It gives rise to delayed hypersensitivity.

BCG vaccine Complications:

  • Local abscess, indolent ulcer, keloid, confluent lesion, lipid lesion.
  • Regional enlargement and suppuration of draining lymph nodes.
  • Systemic fever, mediastinal adenitis.
  • Erythema nodosum.

BCG vaccine Contraindications:

  • In patients of AIDS, Eczema, pertussis, measles, and patients on steroids.

Role of BCG:

  • Makes the disease milder.
  • Prevents serious forms of disease.

Mycobacterium Tuberculosis Short Question And Answers

Question 1. Classification of mycobacteria.
Answer:

Classification of mycobacteria is as follows:

1. Cultivable:

Mycobacterium Tuberculosis Cultivable

2. Non-cultivable.

  • M.Leprae

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