CSFA Microbiology and Infection Control 5 — Questions and Answers
Question 1: Gram staining differentiates bacteria based on differences in their:
- Capsule composition
- Cell wall peptidoglycan layer thickness (Correct answer)
- Ribosomal subunit size
- Flagellar protein structure
Correct answer: Cell wall peptidoglycan layer thickness
Gram-positive bacteria retain crystal violet due to their thick peptidoglycan cell wall, while gram-negative bacteria decolorize because of their thin layer and outer lipid membrane.
Question 2: Which of the following describes the CORRECT method for removing a contaminated gown in the OR after a case?
- Pull it off over the head and place in general trash
- Unfasten ties, roll the gown inward (contaminated surface inside), and discard in biohazard container (Correct answer)
- Have the circulator pull it off from behind while the scrub holds gloves
- Remove gloves first, then pull the gown off by the sleeves
Correct answer: Unfasten ties, roll the gown inward (contaminated surface inside), and discard in biohazard container
Rolling the gown inward contains contaminated surfaces and prevents self-contamination; it is then discarded as regulated medical waste.
Question 3: Which surgical specialty case would most likely be classified as a clean-contaminated (Class II) wound?
- Inguinal hernia repair with no bowel involvement
- Elective sigmoid colectomy with bowel entered under controlled conditions (Correct answer)
- Exploratory laparotomy for a perforated appendix with peritoneal soilage
- Debridement of an infected pressure ulcer
Correct answer: Elective sigmoid colectomy with bowel entered under controlled conditions
Elective colon surgery with controlled entry into the GI tract without gross spillage meets the criteria for Class II clean-contaminated wounds.
Question 4: Terminal cleaning of the OR after an infectious case should begin with:
- Mopping the floor with a broad-spectrum disinfectant
- Cleaning high-touch surfaces and the surgical field first, then progressing to the floor (Correct answer)
- Fogging the room with aerosolized disinfectant before manual cleaning
- Removing all linens and then using UV-C light irradiation only
Correct answer: Cleaning high-touch surfaces and the surgical field first, then progressing to the floor
OR terminal cleaning proceeds from the surgical field and high-touch surfaces downward to the floor, following a clean-to-dirty top-down approach.
Question 5: Which antiseptic preparation requires a minimum drying and contact time before incision to achieve maximum antiseptic effect and to prevent surgical fire risk?
- Povidone-iodine scrub solution
- Chlorhexidine gluconate with alcohol (e.g., ChloraPrep) (Correct answer)
- Aqueous benzalkonium chloride
- Triclosan-based surgical soap
Correct answer: Chlorhexidine gluconate with alcohol (e.g., ChloraPrep)
Alcohol-based chlorhexidine preparations must dry completely before draping; the alcohol evaporation eliminates fire risk and the drying time ensures antimicrobial efficacy.
Question 6: A patient who is HIV-positive is scheduled for an elective cholecystectomy. Standard Precautions in this case require:
- Placing the patient in airborne isolation and using N95 respirators
- Treating all blood and body fluids as potentially infectious, same as any other patient (Correct answer)
- Scheduling the case last of the day to allow extra terminal cleaning time
- Requiring double-gloving for all personnel involved in the case
Correct answer: Treating all blood and body fluids as potentially infectious, same as any other patient
Standard Precautions treat ALL patients' blood and body fluids as potentially infectious regardless of known diagnosis, so care does not change based on HIV status.
Question 7: Which of the following is the most effective personal protective practice to prevent transmission of microorganisms within the surgical environment?
- Wearing double gloves during all procedures
- Consistent and proper hand hygiene between patient contacts (Correct answer)
- Using gowns and masks during all patient interactions
- Routinely culturing OR surfaces between cases
Correct answer: Consistent and proper hand hygiene between patient contacts
Hand hygiene is consistently identified as the single most effective measure to prevent healthcare-associated infections and microbial cross-transmission.
CSFA Microbiology and Infection Control 5
Gram staining differentiates bacteria based on differences in their: