Question 1

Which two groups of Gram-positive cocci are primarily responsible for the majority of human diseases?

Accepted Answer

Staphylococcus and Streptococcus

Question 2

A patient presents with a localized skin infection characterized by honey-colored crusts. Which organism is most likely responsible, and what is the most common portal of entry?

Accepted Answer

Staphylococcus aureus; broken skin

Question 3

Which of the following best explains why Staphylococcus aureus is more difficult for the immune system to eliminate compared to Streptococcus pyogenes?

Accepted Answer

It possesses more virulence factors that inhibit immune recognition.

Question 4

A child develops impetigo. Which feature would help you distinguish this from folliculitis?

Accepted Answer

Impetigo presents as superficial, honey-colored crusted lesions, while folliculitis involves infection of hair follicles.

Question 5

Which virulence factor of Staphylococcus aureus allows it to evade phagocytosis by neutrophils?

Accepted Answer

Protein A

Question 6

A patient with a history of intravenous drug use develops endocarditis. Which Gram-positive cocci is most likely responsible, and what is the target tissue?

Accepted Answer

Staphylococcus aureus; heart valves

Question 7

In systemic infections, how does Streptococcus pyogenes cause host death?

Accepted Answer

By releasing exotoxins that trigger toxic shock and multi-organ failure

Question 8

Which of the following diseases is most commonly associated with Staphylococcus aureus infection?

Accepted Answer

Boils (furuncles)

Question 9

Which population is at greatest risk for developing severe Streptococcus pyogenes infections?

Accepted Answer

Children and the elderly

Question 10

Which Gram-positive cocci is more likely to cause long-term complications such as rheumatic heart disease?

Accepted Answer

Streptococcus pyogenes

Question 11

Which of the following is the most effective prevention procedure for Staphylococcus aureus infections in a hospital setting?

Accepted Answer

Strict hand hygiene and proper wound care

Question 12

A throat swab is taken from a patient with pharyngitis. Which laboratory test would best confirm a Streptococcus pyogenes infection?

Accepted Answer

Rapid antigen detection test (RADT)

Question 13

Which of the following best describes the difference in treatment between Staphylococcus aureus and Streptococcus pyogenes infections?

Accepted Answer

Staphylococcus aureus often requires beta-lactamase resistant antibiotics due to resistance, while Streptococcus pyogenes is usually sensitive to penicillin.

Question 14

A patient develops necrotizing fasciitis after a minor cut. Which virulence factor is most responsible for the rapid tissue destruction seen in this condition?

Accepted Answer

Streptococcal pyrogenic exotoxins

Question 15

Which of the following equations best represents the relationship between the rate of infection ($$R$$), the number of virulence factors ($$V$$), and host immune response ($$I$$), assuming all other factors are constant?

Accepted Answer

$$R = \frac{V}{I}$$

Question 16

A patient with a prosthetic joint develops a low-grade infection months after surgery. Which Gram-positive cocci is most likely responsible, and what is a key diagnostic feature?

Accepted Answer

Staphylococcus epidermidis; biofilm formation on prosthetic material

Question 17

Which of the following best explains why Streptococcus pyogenes can cause rheumatic fever after a pharyngeal infection?

Accepted Answer

Molecular mimicry between bacterial antigens and host tissues leads to autoimmune reactions.

Question 18

A patient with a skin abscess is treated with penicillin but does not improve. Which is the most likely explanation?

Accepted Answer

The infection is caused by a penicillin-resistant Staphylococcus aureus strain.

Question 19

Which of the following is a common long-term complication of untreated Streptococcus pyogenes pharyngitis?

Accepted Answer

Rheumatic heart disease

Question 20

Which of the following best describes the role of hyaluronidase in Gram-positive cocci infections?

Accepted Answer

It breaks down connective tissue, facilitating the spread of infection.

Study Guide: Gram Positive Cocci (Staphylococcus & Streptococcus) in Anatomy & Physiology

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