CER Microbiology and Infection Control 4 — Questions and Answers
Question 1: Which of the following microorganisms is used as the biological indicator (BI) for validating ETO (ethylene oxide) sterilization?
- Geobacillus stearothermophilus
- Bacillus atrophaeus (subtilis) (Correct answer)
- Staphylococcus aureus
- Mycobacterium terrae
Correct answer: Bacillus atrophaeus (subtilis)
Bacillus atrophaeus (formerly B. subtilis) spores are the standard biological indicator for ETO sterilization validation due to their high resistance to this agent.
Question 2: What is the primary purpose of using enzymatic detergents in the manual cleaning of endoscopes?
- To achieve high-level disinfection of internal channels
- To break down proteins, fats, and carbohydrates in organic soil (Correct answer)
- To neutralize chemical residues from prior disinfectants
- To prevent corrosion of metal endoscope components
Correct answer: To break down proteins, fats, and carbohydrates in organic soil
Enzymatic detergents contain enzymes (proteases, lipases, amylases) that chemically break down organic soil — proteins, fats, and carbohydrates — facilitating their physical removal.
Question 3: In chain-of-infection terminology, 'mode of transmission' for an endoscopy-associated infection most commonly refers to:
- Airborne droplet nuclei
- Direct contact via the contaminated endoscope (contact transmission) (Correct answer)
- Vector-borne transmission through insects
- Common vehicle through contaminated water supply
Correct answer: Direct contact via the contaminated endoscope (contact transmission)
Endoscopy-associated infections are primarily transmitted via direct contact when a contaminated scope comes into contact with mucosal surfaces of a new patient.
Question 4: Which organism has caused the most widely publicized endoscopy-related outbreaks in recent years, largely due to the difficulty of cleaning duodenoscopes?
- Clostridioides difficile
- Carbapenem-resistant Enterobacteriaceae (CRE) (Correct answer)
- Methicillin-resistant Staphylococcus aureus (MRSA)
- Mycobacterium chimaera
Correct answer: Carbapenem-resistant Enterobacteriaceae (CRE)
CRE, particularly carbapenem-resistant Klebsiella pneumoniae, has caused major outbreak clusters linked to duodenoscopes because their elevator mechanism is difficult to adequately clean.
Question 5: The Spaulding classification system categorizes medical devices based on:
- The cost and complexity of the device
- The risk of infection based on the intended use and body site (Correct answer)
- The manufacturer's recommended reprocessing method
- The country of device manufacture
Correct answer: The risk of infection based on the intended use and body site
The Spaulding classification (critical, semi-critical, non-critical) categorizes devices by the level of infection risk associated with how and where they contact the patient.
Question 6: Which personal protective equipment (PPE) is considered MINIMUM required when handling a high-level disinfectant such as glutaraldehyde?
- Gloves only
- Gloves and eye protection only
- Gloves, gown, eye protection, and face shield (Correct answer)
- Surgical mask and gloves only
Correct answer: Gloves, gown, eye protection, and face shield
Handling glutaraldehyde requires gloves, liquid-resistant gown, and eye/face protection (goggles and face shield) due to its irritant and sensitizing properties on skin, eyes, and airways.
Question 7: What does 'MIC' (Minimum Inhibitory Concentration) measure in microbiology?
- The lowest concentration of antimicrobial that prevents visible bacterial growth (Correct answer)
- The maximum safe concentration of disinfectant for patient contact
- The time required to kill 50% of a bacterial population
- The concentration of endotoxins detectable in water
Correct answer: The lowest concentration of antimicrobial that prevents visible bacterial growth
MIC is the lowest concentration of an antimicrobial agent (antibiotic or disinfectant) that inhibits visible growth of a microorganism after overnight incubation.
CER Microbiology and Infection Control 4
Which of the following microorganisms is used as the biological indicator (BI) for validating ETO (ethylene oxide) sterilization?