This document describes Corynebacterium diphtheriae, which causes diphtheria. It is a gram-positive bacillus that appears as thin rods or in angled pairs. It contains characteristic granules and does not form spores or move. C. diphtheriae produces a toxin when lysogenized by a bacteriophage carrying the tox gene. The toxin prevents protein synthesis in host cells and causes the symptoms of diphtheria. Transmission occurs through respiratory droplets or skin contact. Diagnosis involves culture identification and tests to detect toxin production. Immunization uses diphtheria toxoid vaccines while treatment requires antitoxin and antibiotics.

2.  It is thin, slender rods.
 Non capsulated, non motile, non acid fast.
 Gram positive bacilli of varying length with
an average size of 3x o.3 um.
 They frequently possess club-shaped
swelling at one or both ends.
 When dividing, the bacilli snap and bend
abruptly and appear as angle pairs or parallel
rows of 3-4 bacilli (palisades) which resemble
chinese letter.

3.  C. Diphtheria possess granules. These
granules are known as metachromatic
granules or volutin granules or Babes-Ernst
bodies.
 Granules are composed of
polymetaphosphate, and represent energy
storage.
 With Albert stain, the granules stain bluish
black and cytoplasm green.

5.  The source of infection are carriers who
harbours the organism. There is no animal
reservoir.
 Transmission occurs from person to person
by respiratory droplet (aerosolised
nasopharyngeal secretions) or skin contact.
 Cutaneous diphtheria also occurs.
 C. diphtheria is not an invasive organism and
systemic manifestation occurs by production
of toxin (exotoxin).

6.  C. Diphtheria that have been lysogenised
with a bacteriophage (beta-phage) carrying
the tox gene produce exotoxin.
 The toxin consist of two moieties:
 . Fraction A
 . Fraction B
 Toxin enters through receptor mediated
endocytosis.

7. Fraction A: the active moiety.
Fraction B: the binding moiety that mediates
the attachment of toxin to the cells via
receptor.
a). Fraction B – It has got a receptor binding
region and a translocation region.

9. - subunit A then catalyses Adenosine
diphosphate ADP- Ribolysation of EF-2, a
factor necessary for movement of nascent
peptide chains on ribosomes.
- One exotoxin molecule can inactivate the
entire EF-2 content in a cell and thereby host
cell protein, synthesis is completely blocked.

17. - Specific treatment against diphtheria
(antitoxin and antibiotic) should be given
immediately after clinical diagnosis without
waiting for

20. Alberts staining:
Procedure:
- Flood the heat fixed smear with Alberts
staining solution A for 5 minutes.
- Drain the staining solution but do not
wash.
- Flood with solution B and keep for 1-2
minutes.
- Wash carefully under running tap
water,drain, blot dry and examine under oil
immersion objective.

22. For culture the swabs are inoculated on:
- Loefflers serum slope.
- Tellurite Blood Agar
- Blood Agar

23. Loefflers serum slope:
- Growth appears in 6-8 hours.
- If negative the media will have to be
incubated for 24 hours.
- Stain with Alberts Stain, will show the
bacilli with metachromatic granules.

25. Tellurite Blood Agar:
- It takes 2 days for manifestation of
colonies.
- The colonies show characteristics gray
to black colour on tellurite agar.

27. - The identification of an isolate as C.
diphtheriae does not mean that the patient
has diphtheria.
- Diagnosis of diphtheria depends on
showing that the isolate produce diphtheria
toxin
- This can be done either in :
In vivo (animal inoculation)
In vitro ( Eleks test)

28. Subcutaneous test:
- Inject broth from culture into two guinea
pigs 0.8 ml
- One animal given 500 units of antitoxin
before.
- Others no antitoxin.
- Animals not given antitoxin will die.
LEADS TO LOSS OF ANIMALS. SO,WE DO NOT
DO IT PRESENT.

29. Eleks gel precipitation test:
- Tested on the horse serum agar.
- Filter paper impregnated with diphtheria
antitoxin 1000 units/ml.
- positive/Negative/Test strain tested for
immunodiffusion.
- Line of precipitation - Test positive.

32. Immunization:
A. Active immunization.
B. Passive immunization.
C. Combined immunization.
. Schick test

33. a) Single preparation:
These include formol
toxoid, alum precipitated toxoid (APT) and
purified toxoid.
b) Combined preparation:
These consist of
diphtheria toxoid in combination with tetanus
toxoid and killed suspension of pertusis
bacilli.

34. DPT - Triple
Vaccine.
- DPT and oral polio vaccine are given
at the age of 6 weeks .(3 doses of DPT at
least 4 weeks apart).
- Booster dose is given at school entry
at 5-6 years.
- Given by intramuscular route.

36. This is an emergency measure
and to be employed when non immunized
individuals are exposed to infection.
It is given subcutaneously
500-1000 units of antitoxin or
antidiphtheritic serum (ADS).

37. Both active immunization with toxoid and
antitoxin.