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
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 toxigenicity
testing of the organism?
(e) What immunoprophylactic measure will
you take for prevention of the disease?
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.
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 caused
by other Corynebacterium species: C.
ulcerans, C. hemolyticum, and C.
Diphtheria was first described by Hippocrates in the
fifth century BC, and throughout history diphtheria
has been a leading cause of death, primarily among
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.
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
Tellurite Blood Agar
,Loefflers serum slope
Diphtheria Clinical Features
Incubation period 2-5 days
(range, 1-10 days)
May involve any mucous membrane
Classified based on site of infection
pharyngeal and tonsillar
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
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 into
the larynx and trachea can lead to
obstruction of the airway with
subsequent suffocation and death
nodes in the neck
and neck swelling
(producing a "bull
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).
Strain widely used for toxin production Park
Williams 8 strain
Is a heat-labile polypeptide produced during
lysogeny of a phage that carries the "tox”
Inhibits protein synthesis by ADP-
ribosylating elongation factor 2
By infected individuals and asymptomatic
carriers (individuals who are infected but do not
Transmission occurs via inhalation of airborne
respiratory secretions or by direct contact with
infected nasopharyngeal secretions or skin
Rarely, infection can be spread by contact with
objects contaminated by an infected person.
Include absent or incomplete immunization
against diphtheria, overcrowded and/or
unsanitary living conditions, a compromised
Travel to areas where the disease is endemic,
especially in individuals who have not obtained
booster shots (vaccine).
Symptoms and Signs
The symptoms and signs of respiratory diphtheria may
initially 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
Weakness,Headache,Cough,Nasal discharge (that may
contain pus or blood-tinged fluid)
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
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.
Cutaneous diphtheria is characterized by an
initially painful red lesion that eventually becomes
a non-healing ulcer covered with a gray-brown
Infection is only rarely associated with systemic
Virulence tests In Vitro: Elek’s Test
The organism is streaked
on a plate containing low
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
At the zone of equivalence,
a precipitate will form.
Virulence tests :In Vivo: Subcutaneous test
Two guinea pigs of same wt. One
acts as control with diphtheria
Diphtherial overnight culture is
injected subcutaneously in to both
If the stain is virulent the
unprotected one wil die within four
Includes diphtheria antitoxin, antibiotics,
and supportive care .
erythromycin or penicillin
Patients with suspected diphtheria
should be placed in isolation in order to
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
CREATED FOR CLINICAL BASED
LEARNING FOR BASIC STUDENTS
DEEPA BABINTMC KOLLAM