CIC Infectious Disease Processes 5 — Questions and Answers
Question 1: Which scenario best illustrates indirect contact transmission of a pathogen?
- A nurse coughing near a patient without a mask
- A patient shaking hands with a colonized visitor
- A patient touching a contaminated bedside rail and then touching their eyes (Correct answer)
- Sharing the same ventilation system with an infectious patient
Correct answer: A patient touching a contaminated bedside rail and then touching their eyes
Indirect contact transmission occurs when a susceptible host contacts a contaminated intermediate object (fomite) rather than directly contacting an infected person.
Question 2: The minimum number of microorganisms required to establish infection in a susceptible host is called the:
- Minimum inhibitory concentration
- Infectious dose (Correct answer)
- Lethal dose
- Inoculum threshold
Correct answer: Infectious dose
The infectious dose (ID50) is the number of organisms required to cause infection in 50% of exposed susceptible hosts, and varies widely by pathogen.
Question 3: A patient with HIV/AIDS has a CD4 count of 50 cells/µL. Which category of immune compromise does this represent?
- Mild immunosuppression
- Moderate immunosuppression
- Severe immunosuppression (Correct answer)
- Complete immunocompetence
Correct answer: Severe immunosuppression
A CD4 count below 200 cells/µL indicates severe immunosuppression and AIDS, dramatically increasing the risk for opportunistic infections.
Question 4: During an outbreak of norovirus gastroenteritis on a hospital unit, which transmission route is primarily responsible for spread?
- Airborne transmission via droplet nuclei
- Fecal-oral route via contact with contaminated surfaces and hands (Correct answer)
- Vector-borne transmission via insects
- Bloodborne transmission via needlesticks
Correct answer: Fecal-oral route via contact with contaminated surfaces and hands
Norovirus spreads predominantly via the fecal-oral route through contaminated hands, surfaces, and food, requiring only a very low infectious dose (18–1000 viral particles).
Question 5: Which statement correctly differentiates bactericidal from bacteriostatic antimicrobial activity?
- Bactericidal agents slow bacterial growth; bacteriostatic agents kill bacteria
- Bacteriostatic agents inhibit bacterial replication; bactericidal agents kill bacteria directly (Correct answer)
- Both terms refer to the same mechanism of action at different concentrations
- Bacteriostatic agents are only used for gram-positive organisms
Correct answer: Bacteriostatic agents inhibit bacterial replication; bactericidal agents kill bacteria directly
Bacteriostatic drugs inhibit bacterial growth and replication, relying on the host immune system to clear the infection, while bactericidal drugs directly kill bacteria.
Question 6: A newly identified pathogen causes illness in 90% of exposed individuals regardless of immune status. This characteristic best describes high:
- Pathogenicity (Correct answer)
- Virulence
- Infectivity
- Toxigenicity
Correct answer: Pathogenicity
Pathogenicity refers to the proportion of infected hosts who develop clinical disease; a high pathogenicity means most infected individuals become ill.
Question 7: The 'incubation period' is most useful in outbreak investigation for determining:
- Which antibiotic to use for treatment
- The likely time of exposure and potential source (Correct answer)
- Whether to implement airborne precautions
- The case fatality rate of the outbreak
Correct answer: The likely time of exposure and potential source
Working backward from illness onset using the known incubation period allows investigators to identify the likely time and source of exposure.
CIC Infectious Disease Processes 5
Which scenario best illustrates indirect contact transmission of a pathogen?