Nursing Prerequisite – Microbiology with
Lab
3 Credits
Final Assessment Review
(Questions & Solutions)
2025
1
,1. Question:
A clinical laboratory technician uses a staining technique to differentiate
bacteria based on their cell wall composition. Which method is most
commonly employed to distinguish Gram-positive from Gram-negative
organisms?
- A) Ziehl–Neelsen stain
- B) Wright–Giemsa stain
- C) Gram stain
- D) India ink stain
Correct ANS: C) Gram stain
Rationale:
The Gram stain is the standard method that differentiates bacteria by
the structure of their cell wall. Gram-positive bacteria retain the crystal
violet dye and appear purple, whereas Gram-negative bacteria do not,
appearing pink after counterstaining. This differentiation is crucial for
guiding antibiotic therapy in clinical settings.
2. Question:
During a microbiology laboratory exercise, a student is asked to perform
a Kirby–Bauer disk diffusion test. What is the primary purpose of this test
in a clinical microbiology lab?
- A) To measure the minimum inhibitory concentration (MIC) of an
antibiotic
- B) To assess the efficacy of disinfectants
- C) To evaluate the antibiotic susceptibility of a bacterial isolate
- D) To identify bacterial species based on metabolic activity
Correct ANS: C) To evaluate the antibiotic susceptibility of a bacterial
isolate
Rationale:
The Kirby–Bauer disk diffusion test is used to determine the sensitivity
2
, of bacteria to specific antibiotics. By measuring the zone of inhibition
around antibiotic disks, clinicians can select effective antimicrobial
therapies—a critical process for nursing professionals managing
infections.
3. Question:
In a molecular microbiology laboratory, polymerase chain reaction (PCR)
is used to detect bacterial DNA in patient samples. Which aspect of PCR
makes it particularly valuable for diagnosing infections with low organism
counts?
- A) Ability to provide quantitative results
- B) Exponential amplification of specific DNA segments
- C) Requirement for live bacteria
- D) Its capacity to identify protein expression
Correct ANS: B) Exponential amplification of specific DNA segments
Rationale:
PCR amplifies trace amounts of bacterial DNA to detectable levels via
exponential replication. This sensitivity makes PCR a powerful diagnostic
tool for identifying pathogens in samples with low bacterial loads,
thereby assisting in early and accurate treatment decisions.
4. Question:
A lab receives a blood culture from an immunocompromised patient.
After 48 hours of incubation, a bacterial colony is isolated. Which
technique would be most effective to rapidly assess if the organism is a
Gram-negative rod?
- A) DNA sequencing
- B) Electron microscopy
- C) Gram staining
- D) Catalase test
Correct ANS: C) Gram staining
Rationale:
Gram staining rapidly classifies bacteria into Gram-positive or Gram-
3
Lab
3 Credits
Final Assessment Review
(Questions & Solutions)
2025
1
,1. Question:
A clinical laboratory technician uses a staining technique to differentiate
bacteria based on their cell wall composition. Which method is most
commonly employed to distinguish Gram-positive from Gram-negative
organisms?
- A) Ziehl–Neelsen stain
- B) Wright–Giemsa stain
- C) Gram stain
- D) India ink stain
Correct ANS: C) Gram stain
Rationale:
The Gram stain is the standard method that differentiates bacteria by
the structure of their cell wall. Gram-positive bacteria retain the crystal
violet dye and appear purple, whereas Gram-negative bacteria do not,
appearing pink after counterstaining. This differentiation is crucial for
guiding antibiotic therapy in clinical settings.
2. Question:
During a microbiology laboratory exercise, a student is asked to perform
a Kirby–Bauer disk diffusion test. What is the primary purpose of this test
in a clinical microbiology lab?
- A) To measure the minimum inhibitory concentration (MIC) of an
antibiotic
- B) To assess the efficacy of disinfectants
- C) To evaluate the antibiotic susceptibility of a bacterial isolate
- D) To identify bacterial species based on metabolic activity
Correct ANS: C) To evaluate the antibiotic susceptibility of a bacterial
isolate
Rationale:
The Kirby–Bauer disk diffusion test is used to determine the sensitivity
2
, of bacteria to specific antibiotics. By measuring the zone of inhibition
around antibiotic disks, clinicians can select effective antimicrobial
therapies—a critical process for nursing professionals managing
infections.
3. Question:
In a molecular microbiology laboratory, polymerase chain reaction (PCR)
is used to detect bacterial DNA in patient samples. Which aspect of PCR
makes it particularly valuable for diagnosing infections with low organism
counts?
- A) Ability to provide quantitative results
- B) Exponential amplification of specific DNA segments
- C) Requirement for live bacteria
- D) Its capacity to identify protein expression
Correct ANS: B) Exponential amplification of specific DNA segments
Rationale:
PCR amplifies trace amounts of bacterial DNA to detectable levels via
exponential replication. This sensitivity makes PCR a powerful diagnostic
tool for identifying pathogens in samples with low bacterial loads,
thereby assisting in early and accurate treatment decisions.
4. Question:
A lab receives a blood culture from an immunocompromised patient.
After 48 hours of incubation, a bacterial colony is isolated. Which
technique would be most effective to rapidly assess if the organism is a
Gram-negative rod?
- A) DNA sequencing
- B) Electron microscopy
- C) Gram staining
- D) Catalase test
Correct ANS: C) Gram staining
Rationale:
Gram staining rapidly classifies bacteria into Gram-positive or Gram-
3
