Q: Which equation best represents the conversion of fibrinogen to fibrin by coagulase in Staphylococcus aureus?

$$\text{Fibrinogen} \xrightarrow{\text{Coagulase}} \text{Fibrin}$$

Q: Which equation best represents the breakdown of hyaluronic acid by hyaluronidase, facilitating bacterial spread?

$$\text{Hyaluronic Acid} \xrightarrow{\text{Hyaluronidase}} \text{Monosaccharides}$$

Q: Which equation best represents the action of penicillinase produced by Staphylococcus aureus?

$$\text{Penicillin} \xrightarrow{\text{Penicillinase}} \text{Inactive Metabolites}$$

Question 1

Which structural feature of Staphylococcus aureus most directly inhibits opsonization by antibodies, thereby evading phagocytosis?

Accepted Answer

Protein A on the cell surface

Question 2

A patient presents with a fever, vomiting, rash, and low blood pressure after using a super-absorbent tampon. Which toxin is most likely responsible for these symptoms?

Accepted Answer

Toxic shock syndrome toxin

Question 3

Staphylococcus aureus can escape from a fibrin clot it has formed around itself. Which enzyme is responsible for dissolving the fibrin threads?

Accepted Answer

Staphylokinase

Question 4

Which of the following best explains why Group B Streptococcus (GBS) is most pathogenic in newborns?

Accepted Answer

Newborns have not yet formed specific antibodies against GBS capsular antigens

Question 5

A laboratory technician adds a drop of bile to a colony of alpha hemolytic bacteria. The colony dissolves within minutes. What is the most likely identity of the bacterium?

Accepted Answer

Streptococcus pneumoniae

Question 6

Which equation best represents the conversion of fibrinogen to fibrin by coagulase in Staphylococcus aureus?

Accepted Answer

$$	ext{Fibrinogen} \xrightarrow{	ext{Coagulase}} 	ext{Fibrin}$$

Question 7

A child develops a red rash on the chest and body, followed by sloughing of the skin after a pharyngitis episode. Which bacterial feature is most responsible for this complication?

Accepted Answer

Pyrogenic toxins from lysogenized Streptococcus pyogenes

Question 8

Which of the following is a major reason why Streptococcus pyogenes can cause repeated infections in a single individual?

Accepted Answer

Antibodies against M protein of one strain do not protect against other strains

Question 9

Which of the following best describes the pathogenesis of diphtheria toxin?

Accepted Answer

It enzymatically inhibits polypeptide synthesis, leading to cell death

Question 10

A patient with a history of broad-spectrum antibiotic use develops severe diarrhea and pseudomembranous colitis. Which organism is most likely responsible?

Accepted Answer

Clostridium difficile

Question 11

Which equation best represents the breakdown of hyaluronic acid by hyaluronidase, facilitating bacterial spread?

Accepted Answer

$$	ext{Hyaluronic Acid} \xrightarrow{	ext{Hyaluronidase}} 	ext{Monosaccharides}$$

Question 12

Which of the following is a distinguishing feature of Enterococcus compared to other Gram-positive cocci?

Accepted Answer

It grows in 6.5% NaCl and 40% bile salts

Question 13

A patient develops endocarditis after a dental procedure. Which group of bacteria is most likely responsible, and what is the mechanism?

Accepted Answer

Viridans group streptococci; enter bloodstream via lacerations and colonize heart valves

Question 14

Which equation best represents the action of penicillinase produced by Staphylococcus aureus?

Accepted Answer

$$	ext{Penicillin} \xrightarrow{	ext{Penicillinase}} 	ext{Inactive Metabolites}$$

Question 15

Which of the following best explains why Bacillus anthracis is resistant to phagocytosis?

Accepted Answer

It produces a capsule composed of glutamic acid

Question 16

A patient presents with a painless, solid raised nodule on the skin that becomes crusty and forms an eschar. Which disease and organism are most likely involved?

Accepted Answer

Cutaneous anthrax; Bacillus anthracis

Question 17

Which of the following is the most effective prevention strategy for diphtheria in a population?

Accepted Answer

Immunization with DTaP vaccine

Question 18

A patient with diabetes develops cellulitis in the lower extremities. Which organism is most likely responsible, and what is the pathogenesis?

Accepted Answer

Streptococcus pyogenes; breaks through skin barrier and invades deeper tissues

Question 19

Which equation best represents the lysis of red blood cells by streptolysin produced by Streptococcus pyogenes?

Accepted Answer

$$	ext{RBCs} \xrightarrow{	ext{Streptolysin}} 	ext{Lysed RBCs}$$

Study Guide: Pathogenic Gram-Positive Bacteria (Chapter 19)

Study Guide - Practice Questions

Study Guide - Flashcards