CIC Infectious Disease Processes 4 — Questions and Answers
Question 1: Which component of the innate immune system provides the first line of defense against invading pathogens?
- B lymphocytes producing antibodies
- Physical barriers such as intact skin and mucous membranes (Correct answer)
- Memory T cells from prior exposure
- Cytotoxic T lymphocytes
Correct answer: Physical barriers such as intact skin and mucous membranes
Physical and chemical barriers—including intact skin, mucous membranes, and secretions—constitute the body's first line of innate immune defense.
Question 2: A patient with end-stage renal disease on hemodialysis develops a fever and elevated white blood cell count. Their blunted immune response is best described as:
- Autoimmunity
- Immunosuppression due to uremia (Correct answer)
- Normal age-related immune decline
- Acquired immunodeficiency
Correct answer: Immunosuppression due to uremia
Uremia from renal failure causes immunosuppression by impairing neutrophil and lymphocyte function, increasing infection susceptibility.
Question 3: The concept of 'herd immunity' is most relevant to infection prevention when:
- All individuals in a population are treated with prophylactic antibiotics
- A sufficient proportion of a population is immune, reducing pathogen transmission (Correct answer)
- Healthcare workers exclusively receive vaccination
- Pathogen mutation renders the organism less virulent
Correct answer: A sufficient proportion of a population is immune, reducing pathogen transmission
Herd immunity occurs when enough of the population is immune (through vaccination or prior infection) to interrupt transmission chains, protecting susceptible individuals.
Question 4: Which of the following best describes an endogenous source of healthcare-associated infection?
- Pathogen transmitted from another patient via shared equipment
- Patient's own flora causing infection after a procedure (Correct answer)
- Contaminated IV fluid administered during treatment
- Airborne pathogen from a nearby infectious patient
Correct answer: Patient's own flora causing infection after a procedure
Endogenous infections arise from the patient's own resident or transient flora, often introduced to normally sterile sites during invasive procedures.
Question 5: Prions differ fundamentally from other infectious agents because they:
- Are destroyed by standard autoclave sterilization
- Contain only protein and no nucleic acid (Correct answer)
- Are classified as gram-positive organisms
- Replicate using host cell ribosomes like viruses
Correct answer: Contain only protein and no nucleic acid
Prions are misfolded proteins with no nucleic acid (DNA or RNA), making them unique among infectious agents and extremely resistant to standard decontamination.
Question 6: A surgical patient develops a wound infection with Staphylococcus aureus five days postoperatively. The most likely source of this organism is:
- The operating room air supply
- Contaminated surgical instruments
- The patient's own skin flora or a colonized healthcare worker (Correct answer)
- Contaminated irrigation solution
Correct answer: The patient's own skin flora or a colonized healthcare worker
The majority of surgical site infections caused by S. aureus are attributable to the patient's own nasal or skin colonization or transmission from colonized OR personnel.
Question 7: Which term describes a disease that is consistently present at a relatively stable baseline level in a defined geographic area or population?
- Epidemic
- Pandemic
- Endemic (Correct answer)
- Hyperendemic
Correct answer: Endemic
An endemic disease maintains a persistent, expected baseline level of occurrence within a specific geographic area without external importation.
CIC Infectious Disease Processes 4
Which component of the innate immune system provides the first line of defense against invading pathogens?