Micro Cor Dip

8/10/2019 Micro Cor Dip

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Corynebacterium

diphtheriae


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A 4yr old boy was brought to the

emergency ward with fever, sore throat

and thick whitish tonsillar exudates with

a white membrane around nasopharynx

was demonstrated and there was cervical

lymphadnopathy, pallor, tachycardia and

dysnoea

?


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a)what is your Provisional diagnosis ?

(b) Describe the morphology and staining

characters of the aetiological agent ?

(c) Describe the pathogenesis?

(d) Discuss the methods of toxigenicitytesting of the organism?

(e) What immunoprophylactic measure willyou take for prevention of the disease?


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The provisional diagnosis can be Faucial diphtheria

caused by Corynebacterium diphtheriae

What is diphtheriae ?

Diphtheria is a bacterial infectious disease spreading

from person to person by respiratory droplets from the

throat through coughing and sneezing.


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Word diphtheria comes from the Greek

word for leather, which refers to the

tough pharyngeal membrane that is the

clinical hallmark of infection.

Rarely, a similar disease can be cause

by other Corynebacterium species: C.

ulcerans, C. hemolyticum, and C.

pseudotuberculosis.


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HISTORY

Diphtheria was first described by Hippocrates in the

fifth century BC, and throughout history diphtheria

has been a leading cause of death, primarily among

children.

The diphtheria bacterium was first identified in the

1880s by F. Loeffler, and the antitoxin against

diphtheria was later developed in the 1890s.

The development of the first diphtheria toxoid

vaccine occurred in the 1920s, by Von behring and

its subsequent widespread use led to a dramatic

decrease of diphtheria worldwide.


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Describe the morphology and

staining characters of the

aetiological agent ?

Gram- positive, slender rods with

palisade or Chinese letters(V,L)

arrangement with club shape at

one or both ends composed of

polymetaphosphate which serve

as energy storage depots called

Babes-Ernst granules or volutin

or metachromatic granules


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Staining with

Methylene blue

Special stains-

Alberts,Neissers

Ponders

Metachromatic granules

Media-Selective -

Tellurite Blood Agar

(McLeods Hoyles)

raised, translucent,

gray/black colonies

Loefflers serum slo e


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Diphtheria Clinical Features

Incubation period 2-5 days

(range, 1-10 days)

May involve any mucous membrane

Classified based on site of infection

anterior nasal

pharyngeal and tonsillar

laryngeal

cutaneous

ocular

enital


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Infection may lead to respiratory

disease, cutaneous disease or an

asymptomatic carrier state.

There are three biotypes of the

bacterium (gravis, mitis, and

intermedius) capable of producing

diphtheria, though each biotype varies

in the severity of disease it produces


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Disease usually starts as a local

infection of the mucous membranes

causing a membranous pharyngitis.

Local toxin effects result in

degeneration of epithelial cells.

Inflammation, edema, and production of

a pseudomembrane composed of

fibrin clots,leukocytes, and dead

epithelial cells and microorganisms

occurs in the throat.

Extension of this pseudomembrane intothe larynx and trachea can lead toobstruction of the airway withsubsequent suffocation and death


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BULL NECK

Enlarged lymph

nodes in the neck

and neck swelling

(producing a bull

neck appearance)


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The diphtheria toxin may be absorbed and disseminated

via the blood and lymphatic system to other organs distan

from the initial infection,

Leads to more severe systemic sequelae (pathological

conditions resulting from a prior disease, injury, or attack)


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Exotoxin

Strain widely used for toxin production ParkWilliams 8 strainIs a heat-labile polypeptide produced during

lysogeny of a phage that carries the "tox

geneInhibits protein synthesis by ADP-

ribosylating elongation factor 2


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Diphtheria toxin


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Risk factors

Include absent or incomplete immunization

against diphtheria, overcrowded and/or

unsanitary living conditions, a compromised

immune system,

Travel to areas where the disease is endemic,

especially in individuals who have not obtained

booster shots (vaccine).


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Symptoms and Signs

The symptoms and signs of respiratory diphtheria mayinitially be similar to a viral upper respiratory infection,

however, the symptoms become more severe with the

progression of the disease.

The symptoms and signs of respiratory diphtheria may

include the following:

Sore throat ,Fever Hoarseness ,Difficulty

swallowing,Malaise

Weakness,Headache,Cough,Nasal discharge (that may

contain pus or blood-tinged fluid)
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The systemic manifestations of diphtheria are caused by

the effects of the diphtheria toxin and its subsequent

dissemination to other organs away from the initial area

of infection.

Commonly affected organs include the heart and

nervous system, leading to complications such as

inflammation of the heart (myocarditis), cardiac rhythm

and conduction disturbances, muscle weakness,

numbness (nerve), and vision changes.


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Cutaneous diphtheria is characterized by an

initially painful red lesion that eventually becomes

a non-healing ulcer covered with a gray-brown

membrane.

Infection is only rarely associated with systemic

complications.


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Virulence tests In Vitro: EleksTest

The organism is streaked

on a plate containing low

iron.

A filter strip containing anti-

toxin antibody is placed

perpendicular to the streak

of the organism.

Diffusion of the antibody into

the medium and secretion of

the toxin into the medium

occur.

At the zone of equivalence,

a precipitate will form.


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Virulence tests :InVivo: Subcutaneous test

Two guinea pigs of same wt. One

acts as control with diphtheria

antitoxin (18-24hrs)

Diphtherial overnight culture is

injected subcutaneously in to both

If the stain is virulent the

unprotected one wil die within four

days


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Treatment

Includes diphtheria antitoxin, antibiotics,

and supportive care .erythromycinor penicillin

Patients with suspected diphtheria

should be placed in isolation in order to

prevent transmission.

Active immunization is started at 6 week

along wth PT,T(DPT)

Three dose of 4-6 weeks intramuscular.

Booster-18 months,5 yr.

Passive immunization-500-1000 units

Diptheria antitoxin
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