Deck 14: Staphylococci

Question 1

What is the function of protein A in the cell wall of Staphylococcus aureus?

A)To keep the structural integrity of the cell wall and keep out antibiotics
B)To bind the IgG and prevent phagocytosis
C)To bind the IgM and inactivate natural killer cells
D)To block the activation of the complement cascade

Answer 1

B
Protein A is one of several cellular components that have been identified in the cell wall of S.aureus.Probably the most significant role of protein A in infections caused by S.aureus is its ability to bind the Fc portion of IgG.Binding IgG in this manner can block phagocytosis.

Question 2

What disease is an extensive exfoliative dermatitis caused by staphylococcal exfoliative toxin?

A)Bullous impetigo
B)Folliculitis
C)Ritter's disease
D)Toxic shock syndrome

Answer 2

C
Scalded skin syndrome, or Ritter's disease, is an extensive exfoliative dermatitis that occurs primarily in newborns and previously healthy young children.This syndrome is caused by staphylococcal exfoliative or epidermolytic toxin produced by Staphylococcus aureus phage group II, probably present at a lesion distant from the site of exfoliation.

Question 3

What is a rare but potentially fatal multisystem disease characterized by high fever, hypotension, and shock, and it is associated with highly absorbent tampons?

A)Toxic epidermal necrolysis
B)Scalded skin syndrome
C)Bullous impetigo
D)Toxic shock syndrome

Answer 3

D
Toxic shock syndrome is a rare but potentially fatal multisystem disease characterized by high fever, hypotension, and shock.It was first described by Todd in 1978 and was associated with highly absorbent tampon use, although some cases did appear in men, children, and nonmenstruating women.

Question 4

What are the effects of the Panton-Valentine toxin produced by Staphylococcus aureus?

A)It acts on sphingomyelin in the plasma membrane of red blood cells.
B)It kills polymorphonuclear leukocytes.
C)It kills macrophages.
D)It lyses red blood cells, damages platelets and macrophages, and can cause severe tissue damage.

Question 5

Staphylococcal enterotoxin B is linked to:

A)carbuncles.
B)staphylococcal pseudomembranous enterocolitis.
C)food poisoning.
D)toxic shock syndrome.

Question 6

What are the effects of the a-hemolysin produced by Staphylococcus aureus?

A)It acts on sphingomyelin in the plasma membrane of red blood cells.
B)It kills polymorphonuclear leukocytes.
C)It kills macrophages.
D)It lyses red blood cells, damages platelets and macrophages, and can cause severe tissue damage.

Question 7

All of the following virulence factors are associated with Staphylococcus aureus except:

A)enterotoxins.
B)cytolytic toxins.
C)cellular components such as protein A.
D)endotoxins.

Question 8

What is the mechanism by which toxic shock syndrome toxin-1 (TSST-1) causes toxic shock syndrome (TSS)?

A)The bacteria release the toxin into the blood and it goes to the hypothalamus to produce an extremely high fever.
B)The bacteria release the toxin into the gastrointestinal system where phagocytes engulf the bacteria, leaving a pseudomembrane that irritates the colon.
C)The toxin is a superantigen that stimulates T-cell proliferation with production of large amounts of cytokines.
D)All of the above.

Question 9

What are the staphylococcal products that cause diarrhea and vomiting in humans?

A)Enterotoxins
B)Endotoxins
C)Cytolytic toxins
D)Cellular components, such as protein A

Question 10

How do staphylococci spread so easily when infecting the skin?

A)They produce hyaluronidase, which hydrolyzes hyaluronic acid present in the intracellular ground substance that makes up connective tissue.
B)They produce lipase, which melts the fat under the skin, making it easier to spread.
C)The hemolysins kill the white and red blood cells; then the protease liquefies the skin protein, allowing easy penetration for the bacteria.
D)All of the above.

Question 11

Infections caused by Staphylococcus aureus are suppurative, meaning:

A)these infections ooze lymph fluid.
B)the infection is filled with pus and necrotic tissues.
C)the acute inflammatory response gorges the area with red blood cells.
D)the toxins activate the coagulation system, which isolates the infection.

Question 12

The two most common species of coagulase-negative staphylococci are:

A)Staphylococcus aureus and S.epidermidis.
B)S.capitus and S.lugdunensis.
C)S.epidermidis and S.saprophyticus.
D)S.saccharolyticus and S.epidermidis.

Question 13

Staphylococcus aureus food poisoning is most commonly caused by which two enterotoxins?

A)A and D
B)A and B
C)B and C
D)B and D

Question 14

Staphylococci are catalase-positive, gram-positive cocci that resemble other bacteria that are members of what family?

A)Micrococcaceae
B)Streptococcus
C)Escherichia
D)Enterococcus

Question 15

All of the following enzymes are produced by staphylococci except:

A)lipase.
B)hyaluronidase.
C)amylase.
D)protease.

Question 16

Staphylococci resist the action of inflammatory cells by the production of toxins and enzymes, thereby establishing:

A)a focal lesion.
B)an infection.
C)toxic shock syndrome.
D)scalded skin syndrome.

Question 17

What are the effects of the b-hemolysin produced by Staphylococcus aureus?

A)It acts on sphingomyelin in the plasma membrane of red blood cells.
B)It kills polymorphonuclear leukocytes.
C)It kills macrophages.
D)It lyses red blood cells, damages platelets and macrophages, and can cause severe tissue damage.

Question 18

The development of staphylococcal infection is determined by:

A)virulence of the strain.
B)size of the inoculum.
C)status of host's immune system.
D)all of the above.

Question 19

The primary reservoir for staphylococci is:

A)ears.
B)mouth.
C)nares.
D)throat.

Question 20

All of the following staphylococci are coagulase-positive except:

A)Staphylococcus aureus.
B)S.saprophyticus.
C)S.intermedius.
D)S.delphini.

Question 21

Infections by which organism are predominantly hospital acquired, and some predisposing factors include catheterization, medical implantation, and immunosuppressive therapy?

A)Staphylococcus aureus
B)S.intermedius
C)S.epidermidis
D)S.saprophyticus

Question 22

What antibiotic is used for detection of methicillin resistance?

A)Penicillin
B)Methicillin
C)Erythromycin
D)Oxacillin

Question 23

A woman in her 20s goes to her physician complaining of burning upon urination, frequency, and general malaise.Her physician does a urine culture, and it grows out 25,000 colony-forming units (CFU)/mL of a catalase-positive, coagulase-negative, novobiocin-resistant gram-positive cocci.What is the most likely pathogen?

A)Staphylococcus epidermidis
B)S.haemolyticus
C)S.intermedius
D)S.saprophyticus

Question 24

How is Staphylococcus saprophyticus presumptively identified?

A)Latex agglutination test for clumping factor
B)Rabbit plasma test for coagulase
C)Novobiocin susceptibility
D)All of the above

Question 25

What infection occurs secondary to influenza A virus, has a high mortality rate, and occurs among the infants and immunocompromised patients?

A)Gangrene
B)Staphylococcal pneumoniae
C)Staphylococcal meningitis
D)Staphylococcal peritonitis

Question 26

All of the following is used to describe the colonial morphology of Staphylococcus epidermidis except:

A)b-hemolytic.
B)g-hemolytic.
C)white.
D)small to medium.

Question 27

A young, healthy woman was rushed to the hospital with a high fever, hypotension, and shock.She had not been feeling well that day, but her condition progressively worsened throughout the day.She was feeling fine until a couple days after she started menstruating.What condition could this woman be exhibiting?

A)Scalded skin syndrome
B)Toxic epidermal necrolysis
C)Toxic shock syndrome
D)Food poisoning

Question 28

Which staphylococcal species is associated with urinary tract infections in young, sexually active females?

A)Staphylococcus aureus
B)S.intermedius
C)S.epidermidis
D)S.saprophyticus

Question 29

Later in the evening, after attending a family reunion, several family members went to the emergency department after experiencing nausea, vomiting, abdominal pain, and severe cramping.When questioned about the food at the family reunion, the menu included fried chicken, hot dogs, hamburgers, potato salad, deviled eggs, éclairs, and cheesecake.The symptoms appeared about 4 hours after they ate.What is the most probable explanation for these symptoms?

A)Staphylococcal food poisoning
B)Toxic shock syndrome
C)Toxic epidermal necrolysis
D)Scalded skin syndrome

Question 30

Automated antimicrobial susceptibility testing methods are not reliable in detecting these resistant staphylococci.What antibiotic are the bacteria resistant to?

A)Vancomycin
B)Erythromycin
C)Clindamycin
D)All of the above

Question 31

What tests are used to detect clumping factor that differentiates Staphylococcus aureus from other staphylococcal species?

A)Novobiocin and hemolysin A
B)Coagulase and latex agglutination
C)Complement fixation and coagulase
D)Latex agglutination and enzyme immunoassay (EIA)

Question 32

Which staphylococcus produces wide zones of beta hemolysis on 5% sheep blood agar?

A)Staphylococcus epidermidis
B)S.aureus
C)S.intermedius
D)S.saprophyticus

Question 33

Colony characteristics for Staphylococcus aureus on blood agar after 18 to 24 hours incubation at 35° C include all the following except:

A)swarming.
B)smooth.
C)white.
D)round.

Question 34

A young man goes to his physician complaining of large, raised, suppurative abscesses on his neck.The man denies having a fever or the chills.What is the name of the lesions on his neck, and what organism causes this type of lesions?

A)Staphylococcus epidermidis and boils
B)S.aureus and furuncles
C)S.saprophyticus and carbuncles
D)S.sciuri and folliculitis