Nursing Bacterial Diseases 2026 Practice Test
Questions: Detailed Rationales on Pathogens,
Infection Manifestations, Transmission,
Prevention, Laboratory Identification, and
Clinical Care
Section 1: Bacterial Pathogens and Classification (Questions 1–25)
1. A nurse is reviewing bacterial classification. Which type of bacteria appears
purple under Gram stain?
A. Gram-negative
B. Gram-positive
C. Acid-fast
D. Spirochete
Rationale: Gram-positive bacteria retain the crystal violet stain and appear purple
under the microscope due to their thick peptidoglycan layer. Gram-negative
bacteria appear pink/red.
2. A nurse is teaching about bacterial shapes. Which term describes rod-
shaped bacteria?
A. Cocci
B. Bacilli
C. Spirilla
D. Vibrios
Rationale: Bacilli are rod-shaped bacteria. Cocci are spherical, spirilla are spiral-
shaped, and vibrios are comma-shaped.
3. Which bacterial structure is responsible for attachment to host cells?
A. Flagella
B. Pili (fimbriae)
C. Capsule
D. Spore
,Rationale: Pili (fimbriae) are hair-like structures that mediate attachment to host
cell receptors. Flagella provide motility, capsules protect against phagocytosis, and
spores are dormant survival structures.
4. A nurse is reviewing aerobic and anaerobic bacteria. Which term describes
bacteria that grow best in low oxygen concentrations?
A. Obligate aerobe
B. Obligate anaerobe
C. Facultative anaerobe
D. Microaerophilic
Rationale: Microaerophilic bacteria grow best in low oxygen concentrations.
Obligate aerobes require oxygen, obligate anaerobes grow only without oxygen,
and facultative anaerobes can grow with or without oxygen.
5. A nurse is teaching about bacterial spores. Which genus produces spores
that are highly resistant to heat and disinfectants?
A. Staphylococcus
B. Streptococcus
C. Clostridium
D. Escherichia
Rationale: Clostridium and Bacillus species produce endospores that are highly
resistant to heat, radiation, and disinfectants.
6. A nurse is reviewing the structure of gram-negative bacteria. Which
component is found in the outer membrane and acts as an endotoxin?
A. Peptidoglycan
B. Lipopolysaccharide (LPS)
C. Teichoic acid
D. Capsule
Rationale: Lipopolysaccharide (LPS) is found in the outer membrane of gram-
negative bacteria and acts as an endotoxin, causing fever, inflammation, and shock.
7. A nurse is teaching about bacterial capsules. Which is a function of the
capsule?
A. Motility
B. Protection against phagocytosis
C. Attachment to host cells
D. DNA transfer
,Rationale: The capsule is a polysaccharide layer that protects bacteria from
phagocytosis and enhances virulence.
8. A nurse is reviewing bacterial growth phases. During which phase do
bacteria produce toxins and enzymes?
A. Lag phase
B. Log phase
C. Stationary phase
D. Death phase
Rationale: During the log (exponential) phase, bacteria are actively dividing and
producing toxins and enzymes that contribute to disease.
9. A nurse is teaching about acid-fast bacteria. Which organism is acid-fast?
A. Staphylococcus aureus
B. Mycobacterium tuberculosis
C. Escherichia coli
D. Streptococcus pneumoniae
Rationale: Mycobacterium tuberculosis is acid-fast due to the high lipid content
(mycolic acid) in its cell wall, which retains the carbolfuchsin stain.
10. A nurse is reviewing bacterial classification by oxygen requirements.
Which type of bacteria causes gas gangrene?
A. Obligate aerobe
B. Obligate anaerobe
C. Facultative anaerobe
D. Microaerophilic
Rationale: Clostridium perfringens is an obligate anaerobe that causes gas
gangrene in devitalized tissue where oxygen is absent.
11. A nurse is teaching about bacterial virulence factors. Which factor allows
bacteria to evade the immune system?
A. Flagella
B. Capsule
C. Pili
D. Spore
Rationale: The capsule protects bacteria from phagocytosis and complement-
mediated killing, allowing them to evade the immune system.
, 12. A nurse is reviewing the Gram stain procedure. Which reagent is used as
the primary stain?
A. Iodine
B. Crystal violet
C. Safranin
D. Alcohol
Rationale: Crystal violet is the primary stain in the Gram stain procedure. Iodine
is the mordant, alcohol is the decolorizer, and safranin is the counterstain.
13. A nurse is teaching about bacterial toxin production. Which type of toxin
is produced by gram-negative bacteria and causes fever and shock?
A. Exotoxin
B. Endotoxin
C. Enterotoxin
D. Neurotoxin
Rationale: Endotoxins are lipopolysaccharides found in the outer membrane of
gram-negative bacteria. They cause fever, inflammation, and septic shock.
14. A nurse is reviewing bacterial genetics. Which process allows bacteria to
transfer DNA through direct cell-to-cell contact?
A. Transformation
B. Transduction
C. Conjugation
D. Mutation
Rationale: Conjugation is the transfer of DNA between bacteria through direct
cell-to-cell contact via a pilus. Transformation involves uptake of free DNA, and
transduction involves viral transfer.
15. A nurse is teaching about bacterial resistance. Which mechanism allows
bacteria to resist antibiotics?
A. Increased permeability
B. Production of beta-lactamase
C. Loss of capsule
D. Loss of flagella
Rationale: Beta-lactamase is an enzyme that inactivates beta-lactam antibiotics
such as penicillin. Other resistance mechanisms include efflux pumps and altered
target sites.
Questions: Detailed Rationales on Pathogens,
Infection Manifestations, Transmission,
Prevention, Laboratory Identification, and
Clinical Care
Section 1: Bacterial Pathogens and Classification (Questions 1–25)
1. A nurse is reviewing bacterial classification. Which type of bacteria appears
purple under Gram stain?
A. Gram-negative
B. Gram-positive
C. Acid-fast
D. Spirochete
Rationale: Gram-positive bacteria retain the crystal violet stain and appear purple
under the microscope due to their thick peptidoglycan layer. Gram-negative
bacteria appear pink/red.
2. A nurse is teaching about bacterial shapes. Which term describes rod-
shaped bacteria?
A. Cocci
B. Bacilli
C. Spirilla
D. Vibrios
Rationale: Bacilli are rod-shaped bacteria. Cocci are spherical, spirilla are spiral-
shaped, and vibrios are comma-shaped.
3. Which bacterial structure is responsible for attachment to host cells?
A. Flagella
B. Pili (fimbriae)
C. Capsule
D. Spore
,Rationale: Pili (fimbriae) are hair-like structures that mediate attachment to host
cell receptors. Flagella provide motility, capsules protect against phagocytosis, and
spores are dormant survival structures.
4. A nurse is reviewing aerobic and anaerobic bacteria. Which term describes
bacteria that grow best in low oxygen concentrations?
A. Obligate aerobe
B. Obligate anaerobe
C. Facultative anaerobe
D. Microaerophilic
Rationale: Microaerophilic bacteria grow best in low oxygen concentrations.
Obligate aerobes require oxygen, obligate anaerobes grow only without oxygen,
and facultative anaerobes can grow with or without oxygen.
5. A nurse is teaching about bacterial spores. Which genus produces spores
that are highly resistant to heat and disinfectants?
A. Staphylococcus
B. Streptococcus
C. Clostridium
D. Escherichia
Rationale: Clostridium and Bacillus species produce endospores that are highly
resistant to heat, radiation, and disinfectants.
6. A nurse is reviewing the structure of gram-negative bacteria. Which
component is found in the outer membrane and acts as an endotoxin?
A. Peptidoglycan
B. Lipopolysaccharide (LPS)
C. Teichoic acid
D. Capsule
Rationale: Lipopolysaccharide (LPS) is found in the outer membrane of gram-
negative bacteria and acts as an endotoxin, causing fever, inflammation, and shock.
7. A nurse is teaching about bacterial capsules. Which is a function of the
capsule?
A. Motility
B. Protection against phagocytosis
C. Attachment to host cells
D. DNA transfer
,Rationale: The capsule is a polysaccharide layer that protects bacteria from
phagocytosis and enhances virulence.
8. A nurse is reviewing bacterial growth phases. During which phase do
bacteria produce toxins and enzymes?
A. Lag phase
B. Log phase
C. Stationary phase
D. Death phase
Rationale: During the log (exponential) phase, bacteria are actively dividing and
producing toxins and enzymes that contribute to disease.
9. A nurse is teaching about acid-fast bacteria. Which organism is acid-fast?
A. Staphylococcus aureus
B. Mycobacterium tuberculosis
C. Escherichia coli
D. Streptococcus pneumoniae
Rationale: Mycobacterium tuberculosis is acid-fast due to the high lipid content
(mycolic acid) in its cell wall, which retains the carbolfuchsin stain.
10. A nurse is reviewing bacterial classification by oxygen requirements.
Which type of bacteria causes gas gangrene?
A. Obligate aerobe
B. Obligate anaerobe
C. Facultative anaerobe
D. Microaerophilic
Rationale: Clostridium perfringens is an obligate anaerobe that causes gas
gangrene in devitalized tissue where oxygen is absent.
11. A nurse is teaching about bacterial virulence factors. Which factor allows
bacteria to evade the immune system?
A. Flagella
B. Capsule
C. Pili
D. Spore
Rationale: The capsule protects bacteria from phagocytosis and complement-
mediated killing, allowing them to evade the immune system.
, 12. A nurse is reviewing the Gram stain procedure. Which reagent is used as
the primary stain?
A. Iodine
B. Crystal violet
C. Safranin
D. Alcohol
Rationale: Crystal violet is the primary stain in the Gram stain procedure. Iodine
is the mordant, alcohol is the decolorizer, and safranin is the counterstain.
13. A nurse is teaching about bacterial toxin production. Which type of toxin
is produced by gram-negative bacteria and causes fever and shock?
A. Exotoxin
B. Endotoxin
C. Enterotoxin
D. Neurotoxin
Rationale: Endotoxins are lipopolysaccharides found in the outer membrane of
gram-negative bacteria. They cause fever, inflammation, and septic shock.
14. A nurse is reviewing bacterial genetics. Which process allows bacteria to
transfer DNA through direct cell-to-cell contact?
A. Transformation
B. Transduction
C. Conjugation
D. Mutation
Rationale: Conjugation is the transfer of DNA between bacteria through direct
cell-to-cell contact via a pilus. Transformation involves uptake of free DNA, and
transduction involves viral transfer.
15. A nurse is teaching about bacterial resistance. Which mechanism allows
bacteria to resist antibiotics?
A. Increased permeability
B. Production of beta-lactamase
C. Loss of capsule
D. Loss of flagella
Rationale: Beta-lactamase is an enzyme that inactivates beta-lactam antibiotics
such as penicillin. Other resistance mechanisms include efflux pumps and altered
target sites.
