BIOL 203 Introductory Microbiology
Final Assessment Review
Questions & Solutions
2025
©2025
, I. Multiple Choice Questions (10 Questions)
1. Case Study: A 65‑year‑old post‑surgical patient develops a fever and
signs of sepsis. A blood culture later reveals Gram‑positive cocci in
clusters. Which microorganism is most likely responsible for the infection
related to an indwelling catheter?
- A. Staphylococcus aureus
- B. Staphylococcus epidermidis
- C. Streptococcus pyogenes
- D. Enterococcus faecalis
ANS: B
Rationale: Staphylococcus epidermidis is commonly associated with
infections related to indwelling devices due to its ability to form biofilms
on catheter surfaces.
2. Case Study: A cafeteria outbreak causes rapid-onset vomiting and
diarrhea among multiple individuals. The implicated food was reheated
improperly. Which bacterial toxin is most likely responsible for the
patients’ symptoms?
- A. Clostridium perfringens enterotoxin
- B. Bacillus cereus diarrheal toxin
- C. Staphylococcus aureus enterotoxin
- D. Salmonella enterica endotoxin
ANS: C
Rationale: Staphylococcus aureus produces a preformed, heat‑stable
enterotoxin that causes sudden nausea, vomiting, and diarrhea even
when the bacteria are killed by subsequent heating.
3. Case Study: A patient with community‑acquired pneumonia is
treated with a macrolide antibiotic. The nurse studies the drug’s
©2025
, mechanism of action. Macrolides inhibit protein synthesis by binding to
which ribosomal subunit?
- A. 30S
- B. 50S
- C. 70S
- D. 60S
ANS: B
Rationale: Macrolides bind to the 50S ribosomal subunit and inhibit
the translocation step during protein synthesis, thereby halting bacterial
growth.
4. Case Study: A rapid molecular diagnostic test returns a positive result
for a respiratory virus in a patient with flu-like symptoms. Which of the
following is the greatest advantage of using PCR for microbial detection?
- A. It only detects viable organisms
- B. It provides a rapid turnaround time
- C. It is less sensitive than culture
- D. It is specific only for bacterial pathogens
ANS: B
Rationale: Polymerase Chain Reaction (PCR) enables amplification of
specific nucleic acid sequences, offering rapid and highly sensitive
detection—even from non‑viable organisms.
5. Case Study: A nurse reviews a laboratory report where a bacterial
isolate shows resistance to penicillins. Which mechanism is most likely
responsible for this resistance?
- A. Modified ribosomal binding sites
- B. Efflux pump overexpression
- C. Enzymatic degradation via beta‑lactamase
- D. Reduced cell permeability
ANS: C
Rationale: The production of beta‑lactamase enzymes by bacteria
©2025
Final Assessment Review
Questions & Solutions
2025
©2025
, I. Multiple Choice Questions (10 Questions)
1. Case Study: A 65‑year‑old post‑surgical patient develops a fever and
signs of sepsis. A blood culture later reveals Gram‑positive cocci in
clusters. Which microorganism is most likely responsible for the infection
related to an indwelling catheter?
- A. Staphylococcus aureus
- B. Staphylococcus epidermidis
- C. Streptococcus pyogenes
- D. Enterococcus faecalis
ANS: B
Rationale: Staphylococcus epidermidis is commonly associated with
infections related to indwelling devices due to its ability to form biofilms
on catheter surfaces.
2. Case Study: A cafeteria outbreak causes rapid-onset vomiting and
diarrhea among multiple individuals. The implicated food was reheated
improperly. Which bacterial toxin is most likely responsible for the
patients’ symptoms?
- A. Clostridium perfringens enterotoxin
- B. Bacillus cereus diarrheal toxin
- C. Staphylococcus aureus enterotoxin
- D. Salmonella enterica endotoxin
ANS: C
Rationale: Staphylococcus aureus produces a preformed, heat‑stable
enterotoxin that causes sudden nausea, vomiting, and diarrhea even
when the bacteria are killed by subsequent heating.
3. Case Study: A patient with community‑acquired pneumonia is
treated with a macrolide antibiotic. The nurse studies the drug’s
©2025
, mechanism of action. Macrolides inhibit protein synthesis by binding to
which ribosomal subunit?
- A. 30S
- B. 50S
- C. 70S
- D. 60S
ANS: B
Rationale: Macrolides bind to the 50S ribosomal subunit and inhibit
the translocation step during protein synthesis, thereby halting bacterial
growth.
4. Case Study: A rapid molecular diagnostic test returns a positive result
for a respiratory virus in a patient with flu-like symptoms. Which of the
following is the greatest advantage of using PCR for microbial detection?
- A. It only detects viable organisms
- B. It provides a rapid turnaround time
- C. It is less sensitive than culture
- D. It is specific only for bacterial pathogens
ANS: B
Rationale: Polymerase Chain Reaction (PCR) enables amplification of
specific nucleic acid sequences, offering rapid and highly sensitive
detection—even from non‑viable organisms.
5. Case Study: A nurse reviews a laboratory report where a bacterial
isolate shows resistance to penicillins. Which mechanism is most likely
responsible for this resistance?
- A. Modified ribosomal binding sites
- B. Efflux pump overexpression
- C. Enzymatic degradation via beta‑lactamase
- D. Reduced cell permeability
ANS: C
Rationale: The production of beta‑lactamase enzymes by bacteria
©2025
