CER Microbiology and Infection Control 3 — Questions and Answers
Question 1: Which of the following best describes the mechanism by which glutaraldehyde achieves high-level disinfection?
- Oxidizes cell membrane lipids
- Alkylates proteins and nucleic acids, cross-linking cellular components (Correct answer)
- Disrupts proton gradient across the bacterial membrane
- Chelates metal ions required for enzyme function
Correct answer: Alkylates proteins and nucleic acids, cross-linking cellular components
Glutaraldehyde is an alkylating agent that cross-links proteins and nucleic acids within microbial cells, leading to irreversible cellular damage.
Question 2: Standard precautions (formerly universal precautions) require treating blood and body fluids from ALL patients as if they are:
- Culture-positive for MRSA
- Potentially infectious regardless of diagnosis (Correct answer)
- Safe unless the patient has a known bloodborne illness
- Infectious only during invasive procedures
Correct answer: Potentially infectious regardless of diagnosis
Standard precautions apply to all patients regardless of known diagnosis, treating all blood and body fluids as potentially infectious.
Question 3: What is the significance of a 'D-value' (decimal reduction time) in microbiology?
- Time needed to kill 100% of organisms
- Time required to reduce a microbial population by 90% (1 log) (Correct answer)
- Minimum contact time for high-level disinfection
- Dilution ratio for disinfectant preparation
Correct answer: Time required to reduce a microbial population by 90% (1 log)
The D-value is the time required to reduce the number of viable microorganisms by 90% (one log10 reduction) under specified conditions.
Question 4: Which component of the endoscope reprocessing environment presents the greatest ongoing biofilm contamination risk if not properly controlled?
- Automated endoscope reprocessor (AER) interior (Correct answer)
- Storage cabinet shelving
- Personal protective equipment
- Transport container lids
Correct answer: Automated endoscope reprocessor (AER) interior
The interior chambers and tubing of AERs can harbor biofilm if not regularly cleaned, tested, and maintained, potentially recontaminating processed endoscopes.
Question 5: A technician notices that the minimum effective concentration (MEC) test strip result is below the required threshold for the glutaraldehyde solution in use. What is the correct action?
- Continue using the solution until the expiration date
- Discard the solution and prepare a fresh batch (Correct answer)
- Add more glutaraldehyde concentrate to raise concentration
- Extend immersion time to compensate
Correct answer: Discard the solution and prepare a fresh batch
When MEC testing shows the disinfectant is below effective concentration, it must be discarded immediately and replaced with fresh solution — there is no approved remediation.
Question 6: Transient flora on healthcare workers' hands differ from resident flora in that transient flora are:
- More resistant to hand hygiene products
- Loosely attached and easily removed by proper hand washing (Correct answer)
- Present in deep layers of the skin
- Primarily gram-positive organisms
Correct answer: Loosely attached and easily removed by proper hand washing
Transient flora are superficially attached microorganisms picked up through contact and are readily removed with soap and water or hand sanitizer, unlike deeper resident flora.
Question 7: Which infection control principle is violated when a clean endoscope is placed on the same surface where a contaminated scope previously rested without decontamination of that surface?
- Chain of infection disruption
- Contact transmission prevention
- Standard precautions application
- Cross-contamination prevention (Correct answer)
Correct answer: Cross-contamination prevention
Placing a clean endoscope on an undecontaminated surface that held a dirty scope violates cross-contamination prevention principles by allowing indirect transfer of pathogens.
CER Microbiology and Infection Control 3
Which of the following best describes the mechanism by which glutaraldehyde achieves high-level disinfection?