BIOD 171 Microbiology Module 5 – Latest Updated 2025–2026 |
Pathogenic Microbes, Infectious Disease & Antimicrobials
1. Which answer best identifies or explains standard precautions in microbiology and healthcare?
A. handling cultures without hand hygiene
B. recapping contaminated needles routinely
C. treating blood and certain body fluids as potentially infectious and using appropriate barriers
D. using PPE only when infection is already confirmed
Answer: C. treating blood and certain body fluids as potentially infectious and using appropriate
barriers
Rationale: Standard precautions reduce exposure risk regardless of whether infection is known.
2. Which answer best identifies or explains personal protective equipment?
A. a microbial culture medium
B. a substitute for hand hygiene
C. barriers such as gloves, gowns, eye protection, or masks selected according to exposure risk
D. a diagnostic stain
Answer: C. barriers such as gloves, gowns, eye protection, or masks selected according to exposure
risk
Rationale: PPE reduces contact with infectious materials but complements rather than replaces hand
hygiene and safe technique.
3. Which answer best identifies or explains a pathogen?
A. a nonliving disinfectant
B. any microorganism found on healthy skin
C. a microorganism or agent capable of causing disease
D. a host antibody
Answer: C. a microorganism or agent capable of causing disease
Rationale: Pathogens possess the capacity to cause disease under appropriate conditions.
Page 1
,4. Which answer best identifies or explains virulence?
A. the host incubation period only
B. the degree of pathogenicity or disease-causing capacity of an organism
C. the total number of ribosomes
D. the ability to stain purple
Answer: B. the degree of pathogenicity or disease-causing capacity of an organism
Rationale: Virulence describes how effectively or severely a pathogen causes disease.
5. Which answer best identifies or explains a virulence factor?
A. a host antibody
B. an objective lens
C. a disinfectant molecule
D. a microbial trait that promotes colonization, immune evasion, tissue damage, or spread
Answer: D. a microbial trait that promotes colonization, immune evasion, tissue damage, or spread
Rationale: Virulence factors include capsules, adhesins, toxins, enzymes, and other traits that aid
pathogenesis.
6. Which answer best identifies or explains an exotoxin?
A. the lipid A portion of Gram-negative LPS
B. a secreted microbial protein toxin with a specific cellular target or effect
C. a host cytokine
D. a bacterial chromosome
Answer: B. a secreted microbial protein toxin with a specific cellular target or effect
Rationale: Exotoxins are released proteins that may disrupt signaling, protein synthesis, membranes, or
other host functions.
7. Which answer best identifies or explains endotoxin?
A. a host immunoglobulin
B. lipopolysaccharide, especially lipid A, released from Gram-negative outer membranes
C. a secreted protein toxin from every bacterium
D. a viral envelope protein
Answer: B. lipopolysaccharide, especially lipid A, released from Gram-negative outer membranes
Rationale: Lipid A can trigger strong inflammatory responses, fever, hypotension, and shock.
Page 2
, 8. Which answer best identifies or explains an opportunistic pathogen?
A. an organism that can never cause disease
B. an organism that causes disease especially when host defenses are impaired or when it enters an
unusual site
C. a virus that infects bacteria only
D. a normal antibody
Answer: B. an organism that causes disease especially when host defenses are impaired or when it
enters an unusual site
Rationale: Opportunists exploit altered barriers, immune suppression, or access to normally sterile sites.
9. Which answer best identifies or explains normal microbiota?
A. only disease-causing organisms
B. all microorganisms in the environment
C. sterile tissues
D. microorganisms that commonly inhabit body sites without causing disease under normal conditions
Answer: D. microorganisms that commonly inhabit body sites without causing disease under
normal conditions
Rationale: Normal microbiota can provide colonization resistance and metabolic benefits but may
become opportunistic.
10. Which answer best identifies or explains Staphylococcus aureus?
A. a Gram-positive coccus associated with skin and soft-tissue infections and capable of producing
multiple virulence factors
B. a protozoan causing malaria
C. an acid-fast bacillus causing tuberculosis
D. a Gram-negative spirochete causing syphilis
Answer: A. a Gram-positive coccus associated with skin and soft-tissue infections and capable of
producing multiple virulence factors
Rationale: S. aureus commonly colonizes skin or nares and can cause abscesses, cellulitis, bacteremia,
and toxin-mediated disease.
Page 3
Pathogenic Microbes, Infectious Disease & Antimicrobials
1. Which answer best identifies or explains standard precautions in microbiology and healthcare?
A. handling cultures without hand hygiene
B. recapping contaminated needles routinely
C. treating blood and certain body fluids as potentially infectious and using appropriate barriers
D. using PPE only when infection is already confirmed
Answer: C. treating blood and certain body fluids as potentially infectious and using appropriate
barriers
Rationale: Standard precautions reduce exposure risk regardless of whether infection is known.
2. Which answer best identifies or explains personal protective equipment?
A. a microbial culture medium
B. a substitute for hand hygiene
C. barriers such as gloves, gowns, eye protection, or masks selected according to exposure risk
D. a diagnostic stain
Answer: C. barriers such as gloves, gowns, eye protection, or masks selected according to exposure
risk
Rationale: PPE reduces contact with infectious materials but complements rather than replaces hand
hygiene and safe technique.
3. Which answer best identifies or explains a pathogen?
A. a nonliving disinfectant
B. any microorganism found on healthy skin
C. a microorganism or agent capable of causing disease
D. a host antibody
Answer: C. a microorganism or agent capable of causing disease
Rationale: Pathogens possess the capacity to cause disease under appropriate conditions.
Page 1
,4. Which answer best identifies or explains virulence?
A. the host incubation period only
B. the degree of pathogenicity or disease-causing capacity of an organism
C. the total number of ribosomes
D. the ability to stain purple
Answer: B. the degree of pathogenicity or disease-causing capacity of an organism
Rationale: Virulence describes how effectively or severely a pathogen causes disease.
5. Which answer best identifies or explains a virulence factor?
A. a host antibody
B. an objective lens
C. a disinfectant molecule
D. a microbial trait that promotes colonization, immune evasion, tissue damage, or spread
Answer: D. a microbial trait that promotes colonization, immune evasion, tissue damage, or spread
Rationale: Virulence factors include capsules, adhesins, toxins, enzymes, and other traits that aid
pathogenesis.
6. Which answer best identifies or explains an exotoxin?
A. the lipid A portion of Gram-negative LPS
B. a secreted microbial protein toxin with a specific cellular target or effect
C. a host cytokine
D. a bacterial chromosome
Answer: B. a secreted microbial protein toxin with a specific cellular target or effect
Rationale: Exotoxins are released proteins that may disrupt signaling, protein synthesis, membranes, or
other host functions.
7. Which answer best identifies or explains endotoxin?
A. a host immunoglobulin
B. lipopolysaccharide, especially lipid A, released from Gram-negative outer membranes
C. a secreted protein toxin from every bacterium
D. a viral envelope protein
Answer: B. lipopolysaccharide, especially lipid A, released from Gram-negative outer membranes
Rationale: Lipid A can trigger strong inflammatory responses, fever, hypotension, and shock.
Page 2
, 8. Which answer best identifies or explains an opportunistic pathogen?
A. an organism that can never cause disease
B. an organism that causes disease especially when host defenses are impaired or when it enters an
unusual site
C. a virus that infects bacteria only
D. a normal antibody
Answer: B. an organism that causes disease especially when host defenses are impaired or when it
enters an unusual site
Rationale: Opportunists exploit altered barriers, immune suppression, or access to normally sterile sites.
9. Which answer best identifies or explains normal microbiota?
A. only disease-causing organisms
B. all microorganisms in the environment
C. sterile tissues
D. microorganisms that commonly inhabit body sites without causing disease under normal conditions
Answer: D. microorganisms that commonly inhabit body sites without causing disease under
normal conditions
Rationale: Normal microbiota can provide colonization resistance and metabolic benefits but may
become opportunistic.
10. Which answer best identifies or explains Staphylococcus aureus?
A. a Gram-positive coccus associated with skin and soft-tissue infections and capable of producing
multiple virulence factors
B. a protozoan causing malaria
C. an acid-fast bacillus causing tuberculosis
D. a Gram-negative spirochete causing syphilis
Answer: A. a Gram-positive coccus associated with skin and soft-tissue infections and capable of
producing multiple virulence factors
Rationale: S. aureus commonly colonizes skin or nares and can cause abscesses, cellulitis, bacteremia,
and toxin-mediated disease.
Page 3
