Corynebacterium Diphtheriae

Corynebacterium

Question 1. Describe the morphology, cultural characteristic, and laboratory diagnosis of Corynebacterium diphtheria.
Answer:

Corynebacterium Diphtheria:

• Morphology:
  • C. Diphtheria bacillus are thin slender rods.
  • Corynebacterium Diphtheria are gram-positive bacilli.
  • Corynebacterium Diphtheria are pleomorphic, nonsporting, non-motile, and non-capsulated.
  • Corynebacterium Diphtheria Size – approx 3-6 pm x 0.6 – 0.8 pm.
  • Corynebacterium Diphtheria show clubbing at one or both ends.
  • Corynebacterium Diphtheria have intracellular polyphosphate granules known as metachromatic or volutin or Babes-Ernst granules usually situated at the poles of bacilli.
  • Corynebacterium Diphtheria are arranged in pairs or small groups.
  • Corynebacterium Diphtheria frequently remains attached after division, which gives them Chinese letter or cuneiform arrangement.
  • The granules represent energy storage depots.

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Corynebacterium Diphtheria Cultural Characteristics:

• C. Diphtheria grows at a temperature of 37°C and pH – 7.3.

Corynebacterium Laboratory Diagnosis:

1. Corynebacterium Direct Microscopy.

• Gram staining.
  • Shows gram-positive bacilli.
• Albert staining.
  • Shows beaded slender green rods in a typical Chinese letter pattern.

2. Corynebacterium Culture.

• Loeffler’s serum slope.
  • Growth appears within 6.8 hours of it
• Tellurite blood agar.
  • Incubated at 37°C for at least 48 hours.
• Blood agar.
  • Differentiate streptococcal or staphylococcal pharyngitis.

3. Corynebacterium Biochemical Reactions.

• Corynebacterium ferments carbohydrates like glucose and maltose.
• Corynebacterium reduces NO3.
• Corynebacterium is catalase-positive and oxidase-negative.

4. Corynebacterium Virulence Test: It demonstrates its toxicity.

1. In Vivo Tests:

• Subcutaneous Test:
  • Subcutaneous Methods:
    • Growth from an overnight culture on Loeffler’s slope is emulsified in 2 – 4 ml broth.
    • 0.8 ml of it is injected subcutaneously into two guinea pigs.
    • One of the pigs is protected with prior administration of 500 units of diphtheria antitoxin.
  • Subcutaneous Result:
    • Virulent strains cause the death of unprotected animals within 4 days.
• Intracutaneous Test:
  • Intracutaneous Method:
    • Broth emulsion is injected intracutaneously of about 0.1 ml into two guinea pigs.
    • One of them is protected with 500 units of diphtheria antitoxin – control animal.
    • The test animal is protected with 50 units of diphtheria antitoxin.
  • Intracutaneous Result:
    • Virulent strain causes.
    • Inflammatory reaction at the site of injection which progresses to necrosis in 48 – 72 hours in test animals.
    • No change – in control animal.

2. In Vitro Tests:

• Eleck’s Get Precipitation Test.
  • It is an in vitro immunodiffusion test.
    • Eleck’s Get Precipitation Method:
      • A rectangular strip of filter paper impregnated with diphtheria antitoxin is placed on the surface of a 20% horse serum agar while the medium is still fluid.
      • The surface is dried.
      • Once the agar is set, narrow streaks of the test strains are made at a right angle to the filter paper strip.
      • A positive and negative control is set.
      • The plate is incubated at 37°C for 24 – 48 hours.
    • Eleck’s Get Precipitation Result:
      • Virulent strains produce arrowhead lines of precipitation where the bacterial toxin meets with the antitoxin in optimum concentration.

2. Tissue Culture.

• Tissue Culture demonstrates the toxigenicity of C. diphtheria.
• The toxins produced diffuse into the cells below and kill them.

Question 2. Describe the morphology, pathogenesis, and immunization of Corynebacterium diphtheria.
Answer:

Immunization Of Corynebacterium Pathogenesis:

• The incubation period in diphtheria is 3 – 4 days or maybe as short as 1 day.
• It is most commonly seen in children of 2 – 10 years.
• The sites of infection are:
  • Faucial – common.
  • Laryngeal
  • Nasal
  • Conjunctival
  • Otitic
  • Vulvovaginal
  • Cutaneous.
• It causes local as well as systemic effects.
• Cutaneous diphtheria may be present as a simple pustule or chronic non-healing ulcer.

1. Immunization Of Corynebacterium Local Effects:

2. Immunization Of Corynebacterium Systemic Effects:

• Diphtheria toxin diffuses into the bloodstream and causes toxemia.
• It acts systematically on the cells of cardiac tissue, adrenal, and nerve endings.
• Complications associated with tissue damage at.
  • Heart – Cardiac dysfunction, myocarditis, and circulatory shock.
  • Nervous System – Demyelination, paralysis of throat muscle, and polyneuritis.

Immunization:

1. Active Immunization:

• It is started at 6 weeks of age by toxoid in combination with tetanus toxoid and pertussis vaccine (DPT].
• It is given by intramuscular route.
  • First dose      – 6 weeks
  • Second dose – 10 weeks
  • Third dose     – 14 weeks
  • Booster dose   – 18 months and 5 years

2. Passive Immunization.

• It is an emergency measure
• It consists of subcutaneous administration of 500 – 1000 units of antitoxin or antidiphtheric serum (ADS).
• Used in susceptible exposed to infection.

3. Combined Immunization.

• It should be given to all persons receiving ADS as prophylactic measures.
• It consists of an alum-containing preparation like an alum-precipitated toxoid.

Corynebacterium Short Question And Answers

Question 1. Name two media used for the cultivation of diphtheria.
Answer:

Media used for the cultivation of diphtheria are.

1. Loeffler’s serum slope.
2. Tellurite blood agar.
3. Hiss’s serum water.

Question 2. Name different species of the genus corynebacterium.
Answer:

Various species of the genus Corynebacterium are:

1. C. Diphtheria.
2. C. ulcerans.
3. C. Minutissimum.
4. C. Tenuis.
5. C. Pseudodiphtheriticum.
6. C. Parvum.

Question 3. Staining Of Diphtheria.
Answer:

On staining of diphtheria -with Albert’s stain.

1. Bacilli – looks green.
2. Granules – Appear bluish-black.

Question 4. Types of C.diphtheria.
Answer:

Based on colony morphology, there are 3 types of C. Diphtheria they are as follows.