widal test final

7/30/2019 Widal Test Final

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WIDAL TEST Diagnostic Test for Typhoid Fever



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)



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



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



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



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 )



ANTIGEN

Thermostable somatic (Ohne or O antigen)

Thermolabile flagellar (Hauch or H. Antigen)

Thermolabile capsular (Kapsel or K antigen)



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



ANTIBODY

Anti-O

Anti-H

Anti-K



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.



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



INTERPRETATION

titer to “O” Ag = ACTIVE INFECTION

titer to “H” Ag = PAST INFECTION

titer to “Vi” Ag = CARRIER

titer to all Antigens = MIXED INFECTION



THANK YOU!!!

Roasa, Priscilla Grace

Rubico, Faye Marjorie C.

Salvador, Franz Raniel

Sanchez, CharisseSantos, Samuel

3DMT

widal test final

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