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Presentation Transcript
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Dr. Tola FARAJ Ms. Chnar Hussam
Lecturer and Researcher Research Assistant
____________________________________________________________________________________________ tola.faraj@tiu.edu.iq Immunology Lab.2 Typhoid Fever Widal Test<br>
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Salmonella Typhi (S. Typhi) are bacteria (gram negative, bacillus, motile through the use of multiple flagella) that infect the intestinal tract and the blood.
The disease is referred to as [typhoid fever].
S. Paratyphi bacteria cause a similar, but milder illness, which comes under the same title. Salmonella is one of the most common causes of foodborne disease in the world.<br>
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Typhoidal vs. Non-Typhoidal Salmonella
Salmonella bacteria are classified as either “typhoidal” or “nontyphoidal,” based on their serotype.<br>
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Antigens of Salmonella species_
a. Cell wall O antigen
b. Flagellar H antigen
c. Capsular Vi (Virulence) antigen<br>
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How are typhoid fever and paratyphoid fever spread?
You can get typhoid fever or paratyphoid fever if_
You eat food or drink a beverage that has been touched by a person who is shedding (getting rid of) Salmonella Typhi or Salmonella Paratyphi in their poop and who has not washed their hands thoroughly after going to the bathroom.
Sewage contaminated with Salmonella Typhi or Salmonella Paratyphi gets into water you drink.
Sewage contaminated with Salmonella Typhi or Salmonella Paratyphi gets into water used to rinse food you eat raw.<br>
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What happens if you eat or drink something contaminated with Salmonella Typhi or Salmonella Paratyphi?
The bacteria can multiply and spread into the bloodstream, causing typhoid fever or paratyphoid fever. The portal venous system is responsible for directing blood from parts of the gastrointestinal tract to the liver. Substances absorbed in the small intestine travel first to the liver for processing before continuing to the heart.<br>
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What are the signs and symptoms of typhoid fever and paratyphoid fever? Typhoid fever and paratyphoid fever have similar symptoms̵. People usually have a sustained fever (one that doesn’t come and go) that can be as high as (39–40°C).
Other symptoms of typhoid fever and paratyphoid fever include_
Weakness
Stomach pain
Headache
Diarrhea or constipation
Cough
Loss of appetite
Some people with typhoid fever or paratyphoid fever develop a rash of flat, rose-colored spots.<br>
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Laboratory Diagnosis of Typhoid Fever
Widal Test_
Widal test measures agglutinating antibody levels against O and H antigens. The main principle of widal test is that if antibody is present in patients serum, it will react with respective antigen in the reagent and gives visible clumping on the test card. The antigens used in the test are “H” and “O” antigens of Salmonella Typhi.<br>
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Reagent Composition Ag_ [Febrile Antigen] stabilized suspension of stained killed bacteria in a buffered solution.
CONTROL +ve human serum containing the corresponding febrile antibodies.
CONTROL -ve Agglutinin Control Negative. Non-reactive human serum.<br>
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Storage and Stability Store at 2-8ºC. Do not freeze. Frozen reagents could change the functionality of the test. Antigens and Controls are stable until the expiry date stated on the label. Reading
Nonreactive: Smooth suspension with no visible agglutination.
Reactive: Any degree of agglutination visible macroscopically.<br>
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Sources Of Error
Antigens used beyond their expiry dates may give false negative reactions.
Bacterial contamination of antigens, specimens or saline solution, as well as the freezing of the suspensions may lead to false positive results<br>
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Thank You
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