CH 14 - Streptococcus Infections

Question 1

S. pyogenes is the most common causative agent of all the following disorders and complications except:

• Gastroenteritis
• Pharyngitis
• Scarlet fever
• Impetigo

Answer 1

Gastroenteritis

Question 2

All the following characteristics are descriptive of M protein except:

• Found in association with the hyaluronic capsule
• Inhibits phagocytosis
• Antibody against M protein provides type-specific immunity)
• No known biological role

Answer 2

No known biological role

Question 3

Substance produced by S. pyogenes include all the following except:

• Hyaluronidase
• DNases (A, B, C, D)
• Interferon
• Erythrogenic toxin

Answer 3

Interferon

Question 4

Laboratory diagnosis of S. pyogenes can be made by all the following except:

• Febrile agglutinins
• Culturing of throat or nasal specimens
• ASO procedure
• Anti–DNase B

Answer 4

Febrile agglutinins

Question 5

False ASO results may be caused by all the following except:

• Bacterial contamination of the serum specimen
• Oxidation of ASO reagent caused by shaking or aeration of the reagent vial
• Room temperature reagents and specimens at the time of testing
• The presence of beta-lipoprotein

Answer 5

Room temperature reagents and specimens at the time of testing

Question 6

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

Answer 6

Beta-

Question 7

Long-term complications of S. pyogenes infection can include:

Answer 7

1. Acute rheumatic fever

AND

2. Poststreptococcal glomerulonephritis

Question 8

Particularly virulent serotypes of S. pyogenes produce proteolytic enzymes that cause __________________ in a wound or lesion on an extremity.

Answer 8

Necrotizing fasciitis

Question 9

Hyaluronidase produced by group A streptococci:

Answer 9

Is called spreading factor

Question 10

Streptokinase produced by group A streptococci:

Answer 10

Dissolves clots by converting plasminogen to plasmin

Question 11

Erythrogenic toxin produced by group A streptococci:

Answer 11

Is responsible for characteristic scarlet fever rash

Question 12

All the following are characteristics of S. pyogenes except:

• It is an uncommon pathogen.
• It has been known to cause foodborne and milkborne epidemics
• It is spread by contact with large droplets produced in the upper respiratory tract
• It occurs most commonly in school-age children

Answer 12

It is an uncommon pathogen.

Question 13

The clinical manifestations of S. pyogenes–associated upper respiratory infection are:

Answer 13

Age dependent

Question 14

The most reliable immunologic test for recent S. pyogenes skin infection is:

Answer 14

Anti–DNase B

Question 15

In the classic ASO titer, a rising titer:

Answer 15

Suggests an increase in the severity of infection

Question 16

In the classic ASO titer, a declining titer:

Answer 16

Is a trend toward recovery

Question 17

In the classic ASO titer, a constant (low) titer:

Answer 17

Suggests a past infection but not a current infection

Question 18

If a streptococcal infection is suspected, but the ASO titer does not exceed the reference range, a(n) _________________ should be performed.

Answer 18

Anti–DNase B test

Question 19

The classic tests to demonstrate the presence of streptococcal infection are:

Answer 19

ASO and anti–DNase B

Question 20

The highest reported levels of sensitivity testing for group A streptococci are in:

Answer 20

Surface (optical) immunoassay