Question 1

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

Accepted Answer

Staphylococcus saprophyticus is susceptible to novobiocin, which can be used as a presumptive identification method. The latex agglutination test for clumping factor and the rabbit plasma test for coagulase are more commonly used to differentiate between Staphylococcus aureus (positive for both tests) and other coagulase-negative staphylococci (negative for both tests).

Question 2

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.

Accepted Answer

The description "F1F1F1S1F1F1F10-hemolytic" does not pertain to the colony morphology of Staphylococcus epidermidis, but rather the hemolysis pattern on blood agar. The other choices (white, nonhemolytic, small to medium) are all possible descriptions of the colony morphology.

Question 3

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

Accepted Answer

The symptoms of high fever, hypotension, and shock, along with a recent menstrual period, suggest toxic shock syndrome (TSS), which is caused by certain types of bacteria, most commonly associated with tampon use during menstruation. Scalded skin syndrome and toxic epidermal necrolysis are severe skin reactions often caused by medication or infections. Food poisoning can cause symptoms such as vomiting, diarrhea, and stomach cramps, but would not typically cause the combination of symptoms described in this scenario.

Question 4

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

Accepted Answer

Staphylococcus epidermidis is a common cause of hospital-acquired infections, especially in patients with catheterization, medical implantation, and immunosuppressive therapy. The other options (S. aureus, S. intermedius, and S. saprophyticus) can also cause infections but are not typically associated with these predisposing factors.

Question 5

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

Accepted Answer

The lesions described (large, raised, suppurative abscesses) are consistent with furuncles, which are commonly caused by Staphylococcus aureus. The other choices either do not match the description of the lesions or do not cause furuncles.

Question 6

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.

Accepted Answer

Staphylococcus aureus typically forms smooth, round, and white colonies on blood agar after 18 to 24 hours of incubation at 35°C. Swarming is not a characteristic of this species.

Question 7

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

Accepted Answer

Automated antimicrobial susceptibility testing methods can sometimes fail to detect staphylococci that are resistant to vancomycin, making manual confirmation tests necessary for accurate results.

Question 8

What antimicrobial agent is used for detection of methicillin resistance?
A) Penicillin
B) Methicillin
C) Erythromycin
D) Oxacillin

Accepted Answer

Oxacillin is the antimicrobial agent used for detection of methicillin resistance. Methicillin is not typically used anymore due to its side effects, and oxacillin is a similar drug that is commonly used in its place. Penicillin and erythromycin are not effective for detecting methicillin resistance.

Question 9

The presence of mecA indicates
A) Staphylococcus epidermidis.
B) sensitivity to tetracycline.
C) resistance to methicillin.
D) vancomycin resistance.

Accepted Answer

The presence of mecA gene indicates resistance to methicillin, which is a beta-lactam antibiotic. This gene is commonly found in Methicillin-resistant Staphylococcus aureus (MRSA) but can also be present in other bacteria such as Staphylococcus epidermidis. However, the presence of mecA alone does not indicate resistance to other antibiotics such as tetracycline or vancomycin.

Question 10

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

Accepted Answer

Staphylococcal pneumonia occurs secondary to influenza A virus and is particularly severe among infants and immunocompromised patients, with a high mortality rate. Gangrene is a bacterial infection that can occur in any tissue and is not specific to influenza or immunocompromised patients. Staphylococcal meningitis and peritonitis are also caused by Staphylococcus bacteria but are not specifically associated with influenza or infants/immunocompromised patients.

Question 11

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

Accepted Answer

The symptoms and the urine culture suggest a urinary tract infection (UTI). The most common pathogen causing UTI in sexually active women is Staphylococcus saprophyticus. It is catalase-positive, coagulase-negative, and novobiocin-resistant, which matches the characteristics of the pathogen found in the urine culture. Choices A, B, and C are also coagulase-negative staphylococci, but they are not commonly associated with UTIs.

Question 12

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

Accepted Answer

Staphylococcus saprophyticus is a common cause of urinary tract infections in sexually active young females. The other staphylococcal species listed (S. aureus, S. intermedius, and S. epidermidis) are not typically associated with UTIs.

Question 13

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

Accepted Answer

The symptoms of nausea, vomiting, abdominal pain, and severe cramping appearing around 4 hours after eating are classic symptoms of Staphylococcal food poisoning, which is commonly caused by consuming food contaminated with toxin-producing Staphylococcus aureus bacteria. The types of food at the family reunion, such as fried chicken and potato salad, can be high-risk foods for Staphylococcal contamination.

Question 14

What is the most common causative agent of pyoderma?
A) Staphylococcus aureus
B) Neisseria gonorrhoeae
C) Clostridium perfringens
D) Haemophilus influenzae

Accepted Answer

Staphylococcus aureus is the most common causative agent of pyoderma, which is a skin infection characterized by the formation of pus.

Question 15

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

Accepted Answer

S. aureus is the only species of Staphylococcus that produces wide zones of beta hemolysis on blood agar. S. epidermidis, S. intermedius, and S. saprophyticus all produce either no hemolysis or only small zones of alpha hemolysis.

Quiz 14: Staphylococci

How is Staphylococcus saprophyticus presumptively identified?

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

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

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?

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

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

What antimicrobial agent is used for detection of methicillin resistance?

The presence of mecA indicates

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

This staphylococcal species is associated with urinary tract infections in young, sexually active females.

What is the most common causative agent of pyoderma?

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