widal test final
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WIDAL TEST Diagnostic Test for Typhoid Fever
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TYPHOID FEVER
Mode of Transmission
- ingestion of contaminated food or through
contaminated hands
Infections
a.) Gastroenteritis
b.)Bacteremia and Extraintestinal infections
c.)Enteric Fever (Typhoid Fever)
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PRINCIPLE
Human serum containing Anti-O and Anti-H
antibodies , visibly agglutinate a suspension of
Salmonella “O” and “H” antigens
Anti-O and Anti-H antibodies were measured using
bacterial suspension of killed Salmonella typhi and
Salmonella paratyphi
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M ATERIALS
Reagents
-Serum
-Salmonella “O” antigens (Groups A, B, C, D)
-Salmonella “H” antigens (Groups a, b, c d)
Glassware and Apparatus
-Serological pipetes, 0.1 mL
-porcelain spot plate
-wooden applicator sticks
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VOLUME OF SAMPLE
Patient’s
Serum
Dilution
0.08 mL 1:200.04 mL 1:40
0.02 mL 1:80
0.01 mL 1:160
0.005 mL 1:320
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PROCEDURE
Observe for agglutination using any good direct light
Tilt the spot plate back and forth and read within 2 minutes
Mix the serum and antigen using a wooden applicator stick
Add one drop of antigen suspension on the Px serum
Dispense the required Px serum on each of the well (Use0.1mL serological pipette )
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ANTIGEN
Thermostable somatic (Ohne or O antigen)
Thermolabile flagellar (Hauch or H. Antigen)
Thermolabile capsular (Kapsel or K antigen)
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Somatic ( “O” Ag)
- body of the organism
-used to detect somatic agglutinins against
Salmonella
- Salmonella “O” Ags (Group A, B, C, D)
- preparation: extracting bacterial cultures using phenol or alcohol
-reaction: fine, compact, not easily dispersed aggregates
Flagellar (“H” Ag)
- appendage of bacteria
- Salmonella “H” Ags (Group A, B, C, D)
- preparation: saline containing 2% formalin
-reaction: loose, floccular, course, easily dispersed aggregates
Capsular (“K” Ag)
- capsule of bacteria
-varieties of “K” Ag (“B”, “L”, “Vi”)
- detection is carried out to confirm enteric
infections
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ANTIBODY
Anti-O
Anti-H
Anti-K
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FEBRILE AGGLUTININS FOUND IN THE SERUM
“O” agglutinins
- They are especially important because the titer of
“o” agglutinins rises earlier in the disease and then
drops faster than “H” agglutinnins. “O”agglutinins
are not effected by immunization.
“H” agglutinins
- They are usually unimportant because the “H” titer
are slow to rise in a disease but remains elevated
for several years. “H” titer increase after
immunization.
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M ANNER OF REPORTING
100% of organism agglutinates = ++++ (+4)
75% of organism agglutinates = +++ (+3)
50% of organism agglutinates = ++ (+2)
25% of organism agglutinates = + (+1)
<25% of organism agglutinates = +- (trace)
No agglutination = 0 (non reactive)
≥ +2 is considered a positive test
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INTERPRETATION
titer to “O” Ag = ACTIVE INFECTION
titer to “H” Ag = PAST INFECTION
titer to “Vi” Ag = CARRIER
titer to all Antigens = MIXED INFECTION
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THANK YOU!!!
Roasa, Priscilla Grace
Rubico, Faye Marjorie C.
Salvador, Franz Raniel
Sanchez, CharisseSantos, Samuel
3DMT