CER Microbiology and Infection Control 5 — Questions and Answers
Question 1: Which water quality is recommended for the FINAL rinse of endoscopes after high-level disinfection to prevent recontamination?
- Tap water filtered through a standard filter
- Sterile water or filtered water meeting AAMI standards (Correct answer)
- Distilled water stored in open containers
- Reverse osmosis water used without additional filtration
Correct answer: Sterile water or filtered water meeting AAMI standards
Sterile water or filtered water meeting AAMI/AORN standards should be used for the final rinse to prevent reintroduction of waterborne microorganisms onto a disinfected scope.
Question 2: An endoscope is identified as 'semi-critical' under the Spaulding classification. What is the MINIMUM required level of reprocessing?
- Intermediate-level disinfection
- High-level disinfection (HLD) (Correct answer)
- Sterilization
- Low-level disinfection with an EPA-registered disinfectant
Correct answer: High-level disinfection (HLD)
Semi-critical items contact mucous membranes or non-intact skin and require at minimum high-level disinfection, which eliminates all microorganisms except high numbers of bacterial spores.
Question 3: Which of the following BEST describes how biofilm protects embedded microorganisms from disinfectants?
- Biofilm organisms produce neutralizing enzymes that degrade chemical disinfectants
- The polysaccharide matrix limits disinfectant penetration and creates a protected microenvironment (Correct answer)
- Biofilm organisms enter a dormant spore state resistant to all chemicals
- Biofilm increases the pH to neutralize acidic disinfectants
Correct answer: The polysaccharide matrix limits disinfectant penetration and creates a protected microenvironment
Biofilm's extracellular polysaccharide matrix acts as a physical barrier that dramatically reduces penetration of disinfectants and creates protected microenvironments where organisms survive.
Question 4: When testing an automated endoscope reprocessor (AER), which type of test verifies that all internal channels of the scope are receiving adequate flow during the reprocessing cycle?
- Biological indicator test
- Channel flow/pressure leak test (Correct answer)
- ATP bioluminescence test
- MEC chemical indicator test
Correct answer: Channel flow/pressure leak test
Channel flow or pressure testing verifies that irrigation fluid is reaching all internal lumens of the endoscope during AER reprocessing, ensuring no blocked channels are missed.
Question 5: Which of the following statements about alcohol (70% isopropyl) as a disinfectant for endoscopes is CORRECT?
- Alcohol achieves high-level disinfection and is appropriate for endoscope HLD
- Alcohol is used as a drying agent after HLD but does not itself provide HLD (Correct answer)
- Alcohol sterilizes endoscope channels when used for 10 minutes
- Alcohol is not recommended for any step in endoscope reprocessing
Correct answer: Alcohol is used as a drying agent after HLD but does not itself provide HLD
Alcohol (70% isopropyl or ethyl) is used to flush channels after rinsing to facilitate drying and inhibit waterborne organism growth, but it does not achieve HLD on its own.
Question 6: A patient is diagnosed with active tuberculosis (TB) after undergoing bronchoscopy. Which characteristic of M. tuberculosis makes it more reprocessing-resistant than most vegetative bacteria?
- Its ability to form endospores under stress
- Its thick, waxy mycolic acid-rich cell wall (Correct answer)
- Its production of beta-lactamase enzymes
- Its formation of a protective capsule
Correct answer: Its thick, waxy mycolic acid-rich cell wall
Mycobacterium tuberculosis possesses a unique waxy cell wall rich in mycolic acids that renders it significantly more resistant to many disinfectants than typical gram-positive or gram-negative vegetative bacteria.
Question 7: According to infection control principles, which action BEST interrupts the 'susceptible host' link in the chain of infection during endoscopy procedures?
- Using sterile water for the final scope rinse
- Ensuring patients receive prophylactic antibiotics before the procedure
- Properly reprocessing endoscopes to eliminate pathogens before patient contact (Correct answer)
- Storing endoscopes in a ventilated cabinet after reprocessing
Correct answer: Properly reprocessing endoscopes to eliminate pathogens before patient contact
Proper endoscope reprocessing targets the 'mode of transmission' and 'infectious agent' links, but presenting a clean scope to the patient effectively protects the susceptible host by eliminating the pathogen before contact.
CER Microbiology and Infection Control 5
Which water quality is recommended for the FINAL rinse of endoscopes after high-level disinfection to prevent recontamination?