Laboratory Activities 6 and 7 – Widal Test

Question 1

is a pathologic process brought about by pathogenic microorganisms in which an extremely high fever is a characteristic manifestation.

Answer 1

Febrile disease

Question 2

An example of febrile illness is [?] caused by microorganisms under the genus Salmonella.

Answer 2

typhoid fever

Question 3

 Widal test is a method that qualitatively detects and quantitatively measures the antibodies in the serum of a patient with typhoid fever. This test includes Salmonella species other than Salmonella typhi by the use of a variety of Salmonella O and H antigens.

Question 4

During the disease, the body responds to this antigenic stimulation by producing antibodies with titers that [?] in early stages to a peak and then [?] until it is undetectable.

Answer 4

increase slowly
gradually fall

Question 5

Diseases characterized by fever caused by bacterial microorganisms that include:

Answer 5

o Typhoid fever o Paratyphoid fever o Brucellosis o Tularemia o Typhus

Question 6

Antibodies to Salmonella may be detected in the patient’s serum from the

Answer 6

second week after the onset of infection

Question 7

are antibodies produced in response to various fever-producing bacteria

Answer 7

Febrile agglutinins

Question 8

Febrile Diseases
Includes the following conditions

Answer 8

TYPHOID FEVER
TYPHUS FEVER

Question 9

Salmonella infection

Answer 9

TYPHOID FEVER

Question 10

Rickettsial infection (Typhus, Rocky Mountain spotted fever, other rickettsial infections)

Answer 10

TYPHUS FEVER

Question 11

Transmission: Ingestion of contaminated food or food products

Answer 11

TYPHOID FEVER
TYPHUS FEVER

Question 12

Associated conditions:
o Gastroenteritis
o Bacteremia and extraintestinal infections
o Enteric fever (Typhoid fever)

Answer 12

TYPHOID FEVER
TYPHUS FEVER

Question 13

Standard technique for the diagnosis of typhoid fever

Answer 13

Culture method

Question 14

TYPHOID FEVER
Laboratory diagnosis:

Answer 14

a. Culture method
b. Widal agglutination test

Question 15

TYPHOID FEVER
Laboratory diagnosis:

Question 16

TYPHUS FEVER
Laboratory diagnosis:

Answer 16

a. Weil-Felix Agglutination
b. Rickettsial antibodies

Question 17

a. Culture method Specimens

Answer 17

blood, urine, stool

Question 18

Principle: Bacterial agglutination that detects antibodies in typhoid fever, tularemia, and brucellosis

Answer 18

Widal agglutination test

Question 19

o Antibody of the patient’s serum is measured by adding a constant amount of antigen (i.e., Salmonella species antigens) to serially diluted serum ® After appropriate incubation, the tubes are examined for visible agglutination

Answer 19

Widal agglutination test: Bacterial agglutination

Question 20

Widal agglutination test
Measures the presence of anti-O and anti-H antibodies using bacterial suspensions using:

Answer 20

o Killed Salmonella typhi and Salmonella paratyphi that have been treated to retain O and H antigens
o Brucella abortus (for tularemia and brucellosis)

Question 21

Measures the presence of anti-O and anti-H antibodies using bacterial suspensions

Answer 21

Widal agglutination test

Question 22

Widal agglutination test
Antibodies detected:
o Antibodies to O = _______________ (IgG or IgM?)
o Antibodies to H = _______________ (IgG or IgM?)

Answer 22

o Antibodies to O = _______________ (IgG or IgM?)
o Antibodies to H = _______________ (IgG or IgM?)

Question 23

Widal agglutination test
Interpretation of results:
0
1+
2+
3+
4+

Answer 23

0 No agglutination
1+ 25% agglutination
2+ 50% agglutination
3+ 75% agglutination
4+ 100% agglutination

Question 24

Note: A single rapid slide test is NOT considered positive unless a value of at least [?] is assigned in a sample taken in the [?] of infection

Answer 24

2+
first 2-3 weeks

Question 25

• Qualitative test to detect IgM and IgG antibodies in the serum of a patient with typhoid fever

Answer 25

Typhidot

Question 26

• Detects serum antibody to antigen dotted on a nitrocellulose membrane

Answer 26

Typhidot

Question 27

• Non-specific rickettsial test based on cross-reacting antibodies induced by some rickettsiaeb.

Answer 27

Weil-Felix Agglutination

Question 28

• Antibodies generated from rickettsial infection cross-react with polysaccharide O antigens of some Proteus species

Answer 28

Weil-Felix Agglutination

Question 29

Weil-Felix Agglutination
Proteus species:

Answer 29

o Proteus OX2 and Proteus OX19:
o Proteus OXK:

Question 30

gold standard for diagnosis of TYPHUS FEVER

Answer 30

Rickettsial antibodies

Question 31

o Various antigens can be employed in slide agglutination tests to screen for febrile agglutinins

Answer 31

Serological Tests for Febrile Agglutinins

Question 32

o If a febrile agglutinin is found, it can be titrated by doubling dilutions of the patient’s serum (i.e., 1:20 through 1:320) and adding a constant amount of bacterial antigen

Answer 32

Serological Tests for Febrile Agglutinins

Question 33

Serological Tests for Febrile Agglutinins
Three controls should be run simultaneously:

Answer 33

(1) antigen control
(2) known positive serum control
(3) known negative serum control