Deck 14: Staphylococci

Question 1

This 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) TSS

Answer 1

D

Question 2

The primary reservoir for staphylococci is

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

Answer 2

C

Question 3

This disease is an extensive exfoliative dermatitis caused by staphylococcal exfoliative toxin.

A) Bullous impetigo
B) Folliculitis
C) Ritter's disease
D) TSS

Answer 3

C

Question 4

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 antimicrobial agents
B) To bind IgG and prevent phagocytosis
C) To bind IgM and inactivate natural killer cells
D) To block the activation of the complement cascade

Question 5

Staphylococcus aureus food poisoning is most commonly caused by these two enterotoxins.

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

Question 6

Staphylococcal enterotoxin B is linked to

A) carbuncles.
B) staphylococcal pseudomembranous enterocolitis.
C) middle ear infections.
D) pneumonia.

Question 7

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

A) a focal lesion.
B) infection disease.
C) TSS.
D) scalded skin syndrome.

Question 8

What are the effects of the $\alpha$ -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 9

What is the mechanism by which toxic shock syndrome toxin-1 (TSST-1) causes 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 10

The two species of coagulase-negative staphylococci most often isolated in clinical laboratories 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 11

All of the following enzymes are produced by staphylococci, except

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

Question 12

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 13

All of the following staphylococci are coagulase-positive, except

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

Question 14

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 leukocytes.
C) It kills epithelial cells.
D) It lyses red blood cells, damages platelets and macrophages, and can cause severe tissue damage.

Question 15

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

A) Enterotoxins
B) Endotoxins
C) Cytolytic toxins
D) Protein A

Question 16

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 17

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

A) enterotoxins.
B) cytolytic toxins.
C) protein A.
D) endotoxins.

Question 18

Staphylococci are catalase-positive, gram-positive cocci that resemble other bacteria and are members of this family.

A) Micrococcaceae
B) Staphylococcaceae
C) Streptococcaceae
D) Enterococcus

Question 19

Why 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 20

What are the effects of the $\alpha$ -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 21

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 22

All of the following is used to describe the colony morphology of Staphylococcus epidermidis, except

A) white.
B) $\beta$ -hemolytic.
C) nonhemolytic.
D) small to medium.

Question 23

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 of days after she started menstruating. What condition could this woman be exhibiting?

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

Question 24

Infections by this 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 25

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

Question 26

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 27

Automated antimicrobial susceptibility testing methods are not reliable in detecting staphylococci resistant to this agent.

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

Question 28

What antimicrobial agent is used for detection of methicillin resistance?

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

Question 29

The presence of mecA indicates

A) Staphylococcus epidermidis.
B) sensitivity to tetracycline.
C) resistance to methicillin.
D) vancomycin resistance.

Question 30

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

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

Question 31

A 20-year-old woman goes to her physician complaining of burning upon urination, frequency, and general malaise. Her physician orders a urine culture, which grew 25,000 colony-forming units (CFU)/mL of a catalase-positive, coagulase-negative, novobiocin-resistant gram-positive coccus. What is the most likely pathogen?

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

Question 32

This 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 33

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. The menu included fried chicken, hot dogs, hamburgers, potato salad, deviled eggs, éclairs, and cheesecake. The symptoms appeared about 4 hours after eating. What is the most probable explanation for these symptoms?

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

Question 34

What is the most common causative agent of pyoderma?

A) Staphylococcus aureus
B) Neisseria gonorrhoeae
C) Clostridium perfringens
D) Haemophilus influenzae

Question 35

This staphylococcus produces wide zones of beta hemolysis on 5% sheep blood agar.

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