2S [LAB]: BAT

Question 1

A serologic test for the presumptive diagnosis of enteric or typhoid fever caused by the Gram-negative bacilli S. typhi

Answer 1

Widal test

Question 2

Principle used in Bacterial agglutination test

Answer 2

Direct agglutination

Question 3

Bacterial agglutination test uses what reagent?

Answer 3

Dye-treated suspensions of bacteria

Question 4

Antibody produced by S. typhi exposure that appears before H abs, and is more significant of active infection

Answer 4

Anti-O Abs

Question 5

Antibody produced by S. typhi exposure that is valuable late in the course of disease where O abs may have disappeared

Answer 5

Anti-H Abs

Question 6

For the early phase of infection, which sample is preferred in Widal Test?

Answer 6

Blood

Question 7

Antigen in S. typhi that is heat-stable

Answer 7

O Ag

Question 8

Antigen in S. typhi that is heat-labile

Answer 8

H Ag

Question 9

Specimens submitted by the patient for the Widal test

Answer 9

Paired sera (acute phase, 2 weeks after)

Question 10

Significant titer for the Widal Test

Answer 10

1:80 (0.02 mL)

Question 11

What grading of agglutination is considered significant and positive in the Widal Test?

Answer 11

2+ (50% of the organisms are agglutinated)

Question 12

If high titers are observed on all antigens, this is interpreted as ___

Answer 12

Mixed infections

Question 13

A non-specific test for the detection of rickettsial fever

Answer 13

Weil-Felix test

Question 14

Antigen used in Weil-Felix Test

Answer 14

Proteus OX species strains

Question 15

One of the most common zoonoes that affect farmers, veterinarians, and slaughterhouse workers

Answer 15

Brucella

Question 16

A Rickettsia species are transmitted to human by arthropod except ___

Answer 16

R. prowazekii

Question 17

Significant titer in Weil-Felix test

Answer 17

1:160 (0.01 mL)

Question 18

Significant titer in Brucella test

Answer 18

1:80 (0.02 mL)

Question 19

OX-K strain of Proteus is the ___ strain

Answer 19

Kingsbury strain

Question 20

The antibodies against Brucella antigens are cross-reactive with ___ agglutinins

Answer 20

Tularemia

Question 21

A high titer of Proteus OX-K suggests what rickettsial infection?

Answer 21

Scrub or Tsutsugamushi fever

Question 22

Brill’s disease, murine typhus, epidemic typhus, and Rocky Mountain Spotted Fever (RMSF) will yield what results in Weil-Felix test?

Answer 22

High titer of OX-19
Weak reaction on OX-2

Question 23

Brucellosis is also known as ___

Answer 23

Malta fever

Question 24

Give the causative agent:

Rocky mountain spotted fever

Answer 24

R. ricketsii

Question 25

Give the causative agent: Murine typhus

Answer 25

R. mooseri

Question 26

Give the causative agent: Epidemic typhus

Answer 26

R. prowazekii

Question 27

Give the causative agent: Brill's disease

Answer 27

R. prowazekii

Question 28

Give the causative agent: Scrub typhus

Answer 28

R. tsutsugamushi

Question 29

Gold standard for the serological diagnosis of RMSF

Answer 29

Indirect immunofluorescence assay (IFA)

Question 30

In Indirect immunofluorescence assay (IFA) for RMSF, how much rise in the antibody titers is considered significant?

Answer 30

4-fold

Question 31

In Weil-Felix test, the OX-19 and OX-2 strains are from which spp.?

Answer 31

P. vulgaris

Question 32

In Weil-Felix test, the OX-K strain is from which spp.?

Answer 32

P. mirabilis

Question 33

T/F: The Weil-Felix test is lacks sensitivity and specificity and should not be relied on

Answer 33

T

Question 34

Most prevalent member of the Typhus group globally

Answer 34

R. prowazekii

Question 35

A serological test based on the interaction between antigens from Proteus OX species strains and cross-reactive agglutinins produced by patients with acute rickettsial infection

Answer 35

Weil-Felix Test

Question 36

All of the following are protective mechanisms against bacteria except: i. Production of antimicrobial defense peptides ii. Phagocytosis iii. Activation of complement iv. Release of lipid A from the bacterial cell

Answer 36

iv

Question 37

All of the following are characteristics of streptococcal M proteins except: i. It is the chief virulence factor of Group A streptococci ii. It provokes an immune response iii. Antibodies to one serotype protect against other serotypes iv. It limits phagocytosis of the organism

Answer 37

iii

Question 38

An ASO titer and a streptozyme test are performed on a patient's serum. The ASO titer is negative, the streptozyme test is positive, and both the positive and negative controls react appropriately. What can you conclude from these test results? i. The ASO is falsely negative ii. The patient has an antibody to a streptococcal exoenzyme other than streptolysin O iii. The patient has not had a previous streptococcal infection iv. The patient has scarlet fever

Answer 38

ii

Question 39

Which of the following applies to acute rheumatic fever? i. Symptoms begin after S. pyogenes infection of the throat or the skin ii. Antibodies to Group A streptococci are believed to cross-react with heart tissue iii. Diagnosis is usually made by culture of the organism iv. All patients suffer permanent disability

Answer 39

ii

Question 40

Which of the following is considered to be nonsuppurative complication of streptococcal infection? i. Acute rheumatic fever ii. Scarlet fever iii. Impetigo iv. Pharyngitis

Answer 40

i

Question 41

All of the following are ways that bacteria can evade host defenses except: i. presence of a capsule ii. Stimulation of chemotaxis iii. Production of toxins iv. Lack of adhesion to phagocytic cells

Answer 41

ii

Question 42

Antibody testing for Rocky Mountain spotted fever may not be helpful for which reason? i. It is not specific ii. It is too complicated to perform iii. It is difficult to obtain a blood specimen iv. Antibody production takes at least a week before detection

Answer 42

iv

Question 43

Which of the following is true regarding exotoxins and endotoxins? i. Both endotoxin and exotoxin are highly immunogenic allowing for the development of protective antibodies and vaccines ii. Endotoxin has targeted activity whereas exotoxins have systemic effects when released iii. Endotoxin is released from the cell wall of dead bacteria, wherein exotoxin is released from live bacteria iv. Both endotoxin and exotoxins bind to specific receptors on a bacterial cell leading to cell lysis

Answer 43

iii

Question 44

Indicator used in bacterial agglutination tests

Answer 44

Dye-treated suspensions of bacteria

Question 45

In Widal test, high or rising titer of which antigen is seen if there is an active infection?

Answer 45

O antigen

Question 46

In Widal test, high or rising titer of which antigen is seen if there is an past infection?

Answer 46

H antigen

Question 47

If one is immunized for S. typhi, which antigen will have a high titer?

Answer 47

H antigen

Question 48

A positive slide method Widal test must be confirmed through ___

Answer 48

Tube method

Question 49

In BAT, what is the starting dilution for the setups?

Answer 49

1:20 (0.08 mL)

Question 50

In BAT, high titers observed on all antigens denote ___

Answer 50

mixed infections

Question 51

Individuals immunized with ___ may develop an agglutination titer to Brucella

Answer 51

Chlorella

Question 52

In cases wherein patients with strong clinical evidence of Brucella infections show a negative result in serum agglutination, what must be done?

Answer 52

Test for blocking antibodies

Question 53

In testing for the presence of blocking antibodies for Brucella, what is added to the antigen serum mixture?

Answer 53

Antihuman globulin