CSFA Microbiology and Infection Control 2 — Questions and Answers
Question 1: Which class of microorganism is MOST resistant to standard sterilization methods and requires extended exposure times or special agents to destroy?
- Gram-negative bacteria
- Bacterial endospores (Correct answer)
- Enveloped viruses
- Gram-positive cocci
Correct answer: Bacterial endospores
Bacterial endospores (e.g., from Clostridium and Bacillus species) are the most resistant life forms and require sporicidal conditions such as autoclaving at 121°C for ≥15 minutes.
Question 2: A surgical site infection (SSI) occurring within 30 days of a procedure, involving only skin and subcutaneous tissue, is classified as:
- Organ/space SSI
- Deep incisional SSI
- Superficial incisional SSI (Correct answer)
- Remote site infection
Correct answer: Superficial incisional SSI
CDC defines a superficial incisional SSI as one occurring within 30 days, involving only skin or subcutaneous tissue at the incision site.
Question 3: When should the surgical hand antisepsis (surgical scrub) be performed?
- Immediately before donning sterile gloves only if gloves are torn
- Before every surgical procedure, prior to gowning and gloving (Correct answer)
- Only when the surgeon's hands are visibly soiled
- After gowning but before gloving
Correct answer: Before every surgical procedure, prior to gowning and gloving
Surgical hand antisepsis must be performed before every procedure and before gowning and gloving to reduce transient and resident flora.
Question 4: Which of the following is an example of a prion-related disease relevant to surgical infection control?
- Clostridium difficile colitis
- Creutzfeldt-Jakob disease (CJD) (Correct answer)
- Methicillin-resistant Staphylococcus aureus (MRSA) infection
- Herpes simplex encephalitis
Correct answer: Creutzfeldt-Jakob disease (CJD)
Creutzfeldt-Jakob disease is caused by prions — misfolded proteins that are resistant to standard sterilization — requiring special instrument handling protocols.
Question 5: In the OR, the zone considered the area of greatest microbial risk to an open wound is:
- The restricted zone outside the sterile field
- Directly over and around the operative site (Correct answer)
- The substerile room adjacent to the OR
- The scrub sink area
Correct answer: Directly over and around the operative site
The area directly over and around the operative site is most critical because airborne or contact contamination here directly threatens the open wound.
Question 6: Which antiseptic agent is contraindicated for use near the eyes, ears, and mucous membranes due to tissue toxicity?
- Povidone-iodine
- Chlorhexidine gluconate (Correct answer)
- Isopropyl alcohol
- Benzalkonium chloride
Correct answer: Chlorhexidine gluconate
Chlorhexidine gluconate is ototoxic and can cause corneal damage, making it contraindicated near the eyes, ears, and mucous membranes.
Question 7: Which method is used to verify that a steam autoclave achieved proper sterilization conditions during a load?
- Chemical indicator class 1 (process indicator tape)
- Biological indicator with Geobacillus stearothermophilus spores (Correct answer)
- Visual inspection of instrument surfaces
- Temperature log printout alone
Correct answer: Biological indicator with Geobacillus stearothermophilus spores
Biological indicators containing Geobacillus stearothermophilus spores are the gold standard for confirming actual sterilization efficacy in steam autoclaves.
