Diphtheria toxin is composed of
an amino terminal catalytic domain A (1–193 amino acids) and carboxyl terminal domain B (194–535 amino acids)
, which is further divided into receptor binding and translocation domains (Fig. 10.2).
What is required for diphtheria toxin production?
The Td-based combined vaccine contains only small amounts of the diphtheria toxoid antigen. However, a high level of purity is necessary for this antigen. The diphtheria toxin is produced by growing Corynebacterium diphtheriae in
a semisynthetic, casein-based medium
in a fermenter.
What does diphtheria toxin do to the human body?
Heart damage
. The diphtheria toxin may spread through your bloodstream and damage other tissues in your body. For example, it can damage your heart muscle, causing such complications as inflammation of the heart muscle (myocarditis). Heart damage from myocarditis may be slight or severe.
Is diphtheria toxin an enzyme?
Diphtheria toxin (an
oncolytic enzyme
still in the experimental stage), catalyzes transfer of the adenosine diphosphate ribose (ADP-ribose) moiety of nicotinamide adenine dinucleotide (NAD) to elongation factor 2. This enzyme halts protein synthesis.
Which organ is affected by diphtheria?
Diphtheria can infect
the respiratory tract
(parts of the body involved in breathing) and skin. In the respiratory tract, it causes a thick, gray coating to build up in the throat or nose. This coating can make it hard to breathe and swallow.
Where is diphtheria most commonly found?
Endemic in many countries in
Asia
, the South Pacific, the Middle East, Eastern Europe and in Haiti and the Dominican Republic. Since 2016, respiratory diphtheria outbreaks have occurred in Indonesia, Bangladesh, Myanmar, Vietnam, Venezuela, Haiti, South Africa, and Yemen.
Where is diphtheria toxin found?
Diphtheria toxin is secreted from
Corynebacterium diphtheriae
as a single polypeptide chain containing two major domains: DT-A, which carries the active site for ADP ribosylation of EF-2, and DT-B, which promotes binding of toxin to cells and the entry of the A chain into the cytosolic compartment.
What is the prevention of diphtheria?
Vaccination. Keeping up to date with recommended vaccines is the best way to prevent diphtheria. In the United States, there are four vaccines used to prevent diphtheria:
DTaP, Tdap, DT, and Td
. Each of these vaccines prevents diphtheria and tetanus; DTaP and Tdap also help prevent pertussis (whooping cough).
How do you test for diphtheria toxin?
A competitive passive hemagglutination assay (cPHA)
easy to perform and a highly sensitive ELISA have been investigated for detection of diphtheria toxin from cultures and from human serum. The sensitivity of the cPHA (8 ng toxin/ml) was high enough to detect toxin in pure cultures containing C. diphtheriae.
Does diphtheria invade the bloodstream?
The toxin produced at the site of the membrane is absorbed into the bloodstream
and then distributed to the tissues of the body. The toxin is responsible for major complications such as myocarditis, polyneuropathies, and nephritis, and can also cause thrombocytopenia.
How does diphtheria toxin cause disease?
Diphtheria toxin is an exotoxin secreted by Corynebacterium, the pathogenic bacterium that causes diphtheria. The toxin gene is encoded by a prophage called corynephage β. The toxin causes the disease in
humans by gaining entry into the cell cytoplasm and inhibiting protein synthesis
.
How is diphtheria toxin regulated?
The tox gene has been shown to be regulated by
the heavy metal ion-activated regulatory element DtxR
. In the presence of divalent heavy metal ions, DtxR becomes activated and binds to a 9 bp interrupted palindromic sequence.
What is the main cause of diphtheria?
Diphtheria is a
serious infection caused by strains of bacteria called Corynebacterium diphtheriae
that make a toxin (poison). It is the toxin that can cause people to get very sick. Diphtheria bacteria spread from person to person, usually through respiratory droplets, like from coughing or sneezing.
How common is diphtheria now?
In the 1920s, there were between 100,000 and 200,000 cases of diphtheria each year with 13,000–15,000 deaths. Because of widespread immu- nization and better living conditions,
diphtheria is now rare in the United States
(during 2004–2017, state health departments reported 2 cases of diphtheria in the United States).
Do adults get diphtheria?
What Is Diphtheria? Diphtheria is a bacterial infection. It spreads easily and happens quickly, and mainly affects the nose and throat. Children under 5 and adults over 60 years old are
particularly at risk for getting it
.
What diphtheria smells like?
Diphtheria is caused by bacterial infection with Corynebacterium diphtheria. Diphtheria usually affects the larynx or the lower and upper respiratory tracts and causes a sore throat. Some patients with diphtheria have a sickening,
sweetish or putrid odour
in their breath (19).
