Deck 16: Streptococcal Infections

Question 1

Most patients who have Streptococcus pyogenes infection begin to demonstrate a rise in antibody titer in

A)2 days.
B)7 days.
C)14 days.
D)30 days.

Answer 1

7 days.

Question 2

A characteristic of necrotizing fasciitis is that it

A)is known as the "flesh-eating" bacteria.
B)is caused by Streptococcus pyogenes.
C)destroys the tissue covering the muscles.
D)All of the above.

Answer 2

All of the above.

Question 3

Streptolysin O is

A)nonantigenic.
B)an oxygen-stable enzyme.
C)the most frequently used serologic indicator of an antibody response to a recent streptococcal infection.
D)detected by DNA analysis.

Answer 3

the most frequently used serologic indicator of an antibody response to a recent streptococcal infection.

Question 4

M protein

A)can cause infection, even without strains of S. pyogenes.
B)is a major virulence factor of Streptococcus pyogenes.
C)promotes phagocytosis.
D)is the basis for the subclassification of group B streptococci.

Question 5

M protein contributes to S. pyogenes invasiveness because it

A)neutralizes complement.
B)blocks antigen recognition.
C)blocks an antibody response.
D)impedes phagocytosis.

Question 6

The classic antistreptolysin O (ASO) procedure has been replaced by a(n)

A)optical immunoassay procedure.
B)direct immunofluorescence.
C)radioimmunoassay (RIA).
D)Both A and B.

Question 7

The R antigen found on the fimbriae of pyogens

A)is structurally similar to the M antigen.
B)is immunologically distinct from the M antigen.
C)has no known biologic role.
D)All of the above.

Question 8

An elevated antistreptolysin O (ASO) titer indicates

A)a chronic streptococcal infection.
B)a relatively recent streptococcal infection.
C)carditis of acute rheumatic fever within the past 24 hours.
D)a response to a streptococcal infection within the past 48 hours.

Question 9

Shock-like symptoms can be produced by high levels of

A)antibodies to S. pyogenes.
B)S. pyogenes superantigens.
C)cytokines.
D)Both B and C.

Question 10

A substance that could mediate the fever, shock, and tissue injury observed in patients with STSS is

A)antibody against antistreptolysin O (ASO).
B)M protein.
C)TNF- $\alpha$ .
D)lymphokine.

Question 11

Members of the S. pyogenes species are almost always _____-hemolytic.

A)alpha
B)beta
C)gamma
D)alpha or beta

Question 12

Serologic testing for S. pyogenes should compare acute and convalescent specimens collected ___________ apart.

A)24 hours
B)72 hours
C)1 week
D)3 weeks

Question 13

Important consequences of an S. pyogenes infection include

A)acute rheumatic fever.
B)poststreptococcal glomerulonephritis.
C)rheumatoid arthritis.
D)Both A and B.

Question 14

The portal of entry of streptococci in streptococcal toxic shock syndrome (STSS) cannot be determined in approximately ________ of cases.

A)25%
B)50%
C)75%
D)100%

Question 15

Streptococcus pyogenes is the most common causative agent of

A)pharyngitis.
B)scarlet fever.
C)impetigo.
D)All of the above.

Question 16

Streptolysin S is

A)antigenic.
B)an oxygen-stable enzyme.
C)the most frequently used serologic indicator of an antibody response to a recent streptococcal infection.
D)detected by DNA analysis.

Question 17

Laboratory diagnosis of S. pyogenes can be made by

A)culturing of throat or nasal specimens.
B)an ASO procedure.
C)anti-DNase B (ADN-B).
D)All of the above.

Question 18

Mortality following an outbreak of S. pyogenes that progresses to toxic shock can be as high as

A)25%.
B)50%.
C)70%.
D)90%.

Question 19

The principle of the optical immunoassay involves

A)anti-GAS (antibody) being attached (immobilized) to a thin film.
B)S. pyogenes being attached (immobilized) to a thin film.
C)a color change in the presence of antigen binding.
D)a color change in the absence of antibody binding.

Question 20

The case definition of STSS and necrotizing fasciitis includes

A)serologic confirmation of group A streptococcal infection by a fourfold rise against SLO.
B)serologic confirmation of group A streptococcal infection by a fourfold rise against DNAse B.
C)severe red rash.
D)Both A and B.

Question 21

Match each ASO titer situation to the appropriate description.
Constant (low) titer

A)Current infection
B)Past infection
C)Trend toward recovery
D)Rules out Streptococcus pyogenes infection

Question 22

Match the substance with the correct description.
DNase

A)Is elaborated by scarlet fever-associated strains
B)Also called "spreading factor"
C)Dissolves clots by converting plasminogen to plasmin
D)Four immunologically distinct forms

Question 23

Match the substance with the correct description.
Streptokinase

A)Is elaborated by scarlet fever-associated strains
B)Also called "spreading factor"
C)Dissolves clots by converting plasminogen to plasmin
D)Four immunologically distinct forms

Question 24

Match each ASO titer situation to the appropriate description.
Rising titer

A)Current infection
B)Past infection
C)Trend toward recovery
D)Rules out Streptococcus pyogenes infection

Question 25

Match the substance with the correct description.
Erythrogenic toxin

A)Is elaborated by scarlet fever-associated strains
B)Also called "spreading factor"
C)Dissolves clots by converting plasminogen to plasmin
D)Four immunologically distinct forms

Question 26

Match the substance with the correct description.
Hyaluronidase

A)Is elaborated by scarlet fever-associated strains
B)Also called "spreading factor"
C)Dissolves clots by converting plasminogen to plasmin
D)Four immunologically distinct forms

Question 27

Match each ASO titer situation to the appropriate description.
Declining titer

A)Current infection
B)Past infection
C)Trend toward recovery
D)Rules out Streptococcus pyogenes infection