55. Antitussives, Expectorants and Mucolytics or Therapy of Cough
56. Drugs used in Bronchial Asthema
57. Nasal Decongestants and Cold remedies or Therapy of Allergic Rhinitis
58. Chemotherapy of Tuberculosis
59
Physiology
59. Mechanism and Mechanics of Breathing
60. Regulation of Respiration
61. Pulmonary circulation
62. Pulmonary Gas exchange
63. Gas transport and Exchange
64. Lung compliance
65. Pulmonary Function Tests
66. Spirometry
67. Applied Respiratory Physiology
68. Abnormal Breathing
69. Artificial Respiration
70. Lung Defense Mechanism
71
Microbiology
23. Corynebacterium diphtheria
HISTORY
Klebs and Loeffler discovered it. So it is also called Klebs-loeffler bacilli.
MORPHOLOGY
Non-capsulated
Non-spore forming
Non-motile
Gram +ve bacilli
Chinese letter or Cuneiform structure
Metachromatic granules present
ALBERT STAIN
+ve Bacteria (@MSC GArden)
Mycobacterium
Spirillum volutans
Corynebacterium diphtheriae
Gardenella vaginalis
Agrobacterium tumefaciens
Granules name
Volutin granules → Discovered in Spirillum volutin bacteria
Babes Ernst granules → Discovered by Babes Ernst
Polar bodies → Due to presence at the poles
Metachromatic granules → Due to blue in color
Metachromatic granules stained with (@PLAN)
Ponder's stain
Loeffler's methylene blue
Albert's stain
Neisser's stain
VIRULENCE FACTORS
Diphtheria toxin
It is the primary virulence factor responsible for diphtheria.
Toxoid is used for Vaccination.
PATHOGENICITY
Mechanism of Diphtheria toxin
graph TD
1["DP is released into the blood by <i>C. diphtheria</i>"]
2["DT is a polypeptide chain, comprises <br>of two fragments- A (active) and B (binding)."]
3["Fragment B binds to the host cell <br>receptors (such as epidermal growth factor) <br>and helps in entry of fragment A."]
4["Fragment A gets internalized into the cell."]
5["Causes ADP ribosylation of elongation factor 2 (EF-2)."]
6["Inhibtion of translation step of protein synthesis."]
7["Local complication (Respiratory Diphtheria)"]
8["Faucial diphtheria"]
9["Laryngeal diphtheria"]
10["Nasal diphtheria"]
11["Systemic complication"]
12["Neurological manifestation"]
13["Myocarditis"]
1 --> 2
2 --> 3
3 --> 4
4 --> 5
5 --> 6
6 --> 7
7 --> 8
7 --> 9
7 --> 10
6 --> 11
11 --> 12
11 --> 13
CLINICAL MANIFESTATIONS
LABORATORY DIAGNOSIS
The diagnosis of diphtheria is based on the clinical signs and symptoms plus laboratory confirmation.
Laboratory diagnosis is necessary only for:
•
Confirmation of clinical diagnosis
•
Initiation the control measures
•
Epidemiological purposes
Laboratory diagnosis consists of
•
Isolation of the bacilli
•
Toxin demostration
Isolation of Diphtheria bacilli
Specimen collection
A portion of psuedomembrane (if present)
Throat swab (One or two) containing fibrinous exudates (if there is no psuedomembrane)
Nose or skin specimen (if infected)
Direct smear microscopy
Gram staining
Gram +ve bacilli club-shaped
Irregularly stained
3-6 μm in length
Arranged in Chinese letter or cuneiform arrangement (V- or L-shaped)
Albert stain
Appears as green bacilli with bluish black metachromatic granules at the poles
Culture
Culture medium
Enriched media
Hiss serum
Blood agar
Colonies are small, circular, white and sometimes hemolytic (mitis biotype)
Chocolate agar
Loeffler serum slope
Colonies
Small, circular, glistening and white with a yellow tinge
Culture time
6-8 hours
Selective media
Potassium tellurite agar
C. diphtheria reduces tellurite to metallic tellurium which give the colony black color.
Culture time is 48 hours.
Biotyping of C. diphtheria is done on the basis of colony produced here.
Tinsdale tellurite agar
Identification
Biochemical tests
Sugar fermentation test
using Hiss's serum sugar media
Ferments only Glucose and Mannitol
No gas production
Pyrazinamidase test
-ve
Urease test
-ve
Automation tests
VITEK
MALDI-TOF
Toxin demonstration
In vivo tests (Animal inoculation
It is done in guinea pig.
2 guinea pig are selected.
1 is given only Diphtheria toxin while other is given Diphtheria toxin along with anti-toxin.
Death of first one with survival of other is confirmatory test.
In Vitro test
Elek's gel precipitation test
The strain isolated is streaked onto a media containing a filter paper soaked with antitoxin.
One positive and one negative control tests are also done along with strain test
If the strain is toxigenic, it liberates the toxin which diffuses in the agar and meets with the antitoxin to produce an arrow-shaped precipitation band.
