[BAT] BACTERIAL AGGLUTINATION TEST

Question 1

What is bacterial agglutination?

Answer 1

A serologic test where bacterial antigens react with specific antibodies to form visible clumps.

Question 2

What is the principle of bacterial agglutination tests?

Answer 2

It is based on the antigen-antibody reaction that results in visible clumping (agglutination).

Question 3

What are the main bacterial agglutination tests?

Answer 3

Widal test, Weil-Felix test, Brucella agglutination test, and febrile agglutination tests.

Question 4

What is the Widal test used for?

Answer 4

Diagnosis of typhoid fever by detecting antibodies against Salmonella typhi.

Question 5

What antigen-antibody reaction occurs in the Widal test?

Answer 5

Agglutination occurs when patient antibodies bind to Salmonella ‘O’ and ‘H’ antigens.

Question 6

What are the somatic and flagellar antigens in the Widal test?

Answer 6

‘O’ antigen (somatic) and ‘H’ antigen (flagellar) of Salmonella typhi.

Question 7

What is a positive Widal test result?

Answer 7

A significant titer increase (e.g., 1:160 or higher) in paired serum samples.

Question 8

What is the Weil-Felix test used for?

Answer 8

Diagnosis of rickettsial infections using Proteus OX antigen cross-reactivity.

Question 9

Which bacterial strains are used in the Weil-Felix test?

Answer 9

Proteus OX19, OX2, and OXK.

Question 10

What is the principle of the Weil-Felix test?

Answer 10

Indirect agglutination where Proteus antigens cross-react with rickettsial antibodies.

Question 11

What diseases can be diagnosed using the Weil-Felix test?

Answer 11

Epidemic typhus, scrub typhus, and Rocky Mountain spotted fever.

Question 12

What is a positive Weil-Felix test result?

Answer 12

A fourfold rise in titer between acute and convalescent samples.

Question 13

What is the Brucella agglutination test used for?

Answer 13

Diagnosis of brucellosis, a zoonotic bacterial infection.

Question 14

What specimen is used for the Brucella test?

Answer 14

Serum.

Question 15

What type of antigen is used in the Brucella test?

Answer 15

Heat-killed phenolized Brucella antigens.

Question 16

What is a positive Brucella agglutination test result?

Answer 16

A titer of 1:80 or greater indicates infection.

Question 17

What are febrile agglutination tests?

Answer 17

Agglutination tests for detecting bacterial infections causing persistent fever.

Question 18

What bacterial infections are detected using febrile agglutination tests?

Answer 18

Typhoid fever, brucellosis, rickettsial infections, and tularemia.

Question 19

What are the common bacterial febrile antigens used in testing?

Answer 19

Salmonella, Brucella, Proteus, and Francisella species.

Question 20

What is the test for diagnosing typhoid fever?

Answer 20

Widal test.

Question 21

What is the test for diagnosing brucellosis?

Answer 21

Brucella agglutination test.

Question 22

What is the test for diagnosing rickettsial infections?

Answer 22

Weil-Felix test.

Question 23

What is the test for diagnosing tularemia?

Answer 23

Agglutination test using Francisella tularensis antigen.

Question 24

What is the significance of agglutination titer in bacterial agglutination tests?

Answer 24

A rising titer suggests active infection, while a stable titer suggests past exposure.

Question 25

What is the normal titer for a negative Widal test?

Answer 25

Less than 1:80.

Question 26

What does a high and rising Widal titer indicate?

Answer 26

Active typhoid fever.

Question 27

Why is the tube method preferred for confirming bacterial agglutination tests?

Answer 27

It provides a more accurate measurement of antibody levels.

Question 28

What is the significance of an O antibody titer in Widal testing?

Answer 28

Indicates active infection with Salmonella typhi.

Question 29

What is the significance of an H antibody titer in Widal testing?

Answer 29

Indicates past infection, vaccination, or convalescence.

Question 30

What is the difference between active infection and past infection in the Widal test?

Answer 30

High O titer suggests active infection, while a high H titer suggests past exposure.

Question 31

What are the limitations of the Widal test?

Answer 31

False positives, cross-reactivity, and low sensitivity in vaccinated individuals.

Question 32

Why is the Weil-Felix test not highly specific for rickettsial infections?

Answer 32

Proteus species also cross-react with other bacterial infections.

Question 33

How is the Brucella agglutination test performed?

Answer 33

Patient serum is mixed with Brucella antigen, and agglutination is observed.

Question 34

What is the incubation period for brucellosis before antibodies appear?

Answer 34

1-3 weeks.

Question 35

What is the role of cross-reactivity in bacterial agglutination tests?

Answer 35

Cross-reactivity can cause false-positive results with other bacteria.

Question 36

What causes false-positive bacterial agglutination test results?

Answer 36

Prior infections, vaccinations, and non-specific immune reactions.

Question 37

What causes false-negative bacterial agglutination test results?

Answer 37

Low antibody levels, early infection stage, or immune suppression.

Question 38

Why should bacterial agglutination tests be interpreted with clinical correlation?

Answer 38

Clinical symptoms and epidemiological history improve test accuracy.

Question 39

What is the role of serial dilution in bacterial agglutination tests?

Answer 39

It determines the antibody concentration in the sample.

Question 40

What is the endpoint in a bacterial agglutination test?

Answer 40

The highest dilution at which agglutination is still visible.

Question 41

What is the significance of prozone phenomenon in bacterial agglutination tests?

Answer 41

Excess antibodies can prevent visible agglutination, causing false-negative results.

Question 42

How is the Brucella agglutination titer interpreted?

Answer 42

A titer of 1:80 or higher is considered significant.

Question 43

What are heterophile agglutination reactions in bacterial infections?

Answer 43

Antibodies that cross-react with other bacterial antigens.

Question 44

What are confirmatory tests for bacterial infections detected via agglutination tests?

Answer 44

Culture, PCR, and enzyme immunoassays.

Question 45

What are the advantages of slide agglutination tests?

Answer 45

Rapid results, simple procedure, and requires minimal equipment.

Question 46

What are the disadvantages of slide agglutination tests?

Answer 46

Subjective interpretation and lower accuracy compared to the tube method.

Question 47

Why is the tube method more reliable than the slide method?

Answer 47

It provides more accurate quantification of antibodies.

Question 48

What is the importance of antigen standardization in bacterial agglutination tests?

Answer 48

Ensures specificity and sensitivity of the test.

Question 49

What precautions should be taken while performing bacterial agglutination tests?

Answer 49

Proper specimen collection, avoiding contamination, and following test protocols.