CSFA Microbiology and Infection Control Questions and Answers — Questions and Answers
Question 1: A patient with suspected Creutzfeldt-Jakob disease (CJD) undergoes a brain biopsy. According to CDC and WHO guidelines, which of the following is the most appropriate method for handling the involved surgical instruments?
- Standard steam sterilization followed by immediate reuse.
- Low-temperature hydrogen peroxide gas plasma sterilization.
- Segregation, followed by either incineration or a combination of chemical soaking and extended steam sterilization cycles. (Correct answer)
- Immediate-use steam sterilization (IUSS) in the sub-sterile room.
Correct answer: Segregation, followed by either incineration or a combination of chemical soaking and extended steam sterilization cycles.
Prions, the causative agents of CJD, are highly resistant to conventional sterilization methods. Guidelines from the CDC and WHO recommend that instruments used on high-infectivity tissue from a known or suspected CJD patient should ideally be incinerated. If not incinerated, they must undergo specific, rigorous decontamination protocols, such as soaking in sodium hydroxide (NaOH) or sodium hypochlorite followed by an extended steam sterilization cycle (e.g., 134°C for 18 to 60 minutes). Standard cycles, IUSS, and gas plasma are ineffective against prions.
Question 2: Which of the following microorganisms is a gram-positive coccus, commonly found on the skin, and is the most frequent cause of surgical site infections (SSIs)?
- Escherichia coli
- Pseudomonas aeruginosa
- Staphylococcus aureus (Correct answer)
- Candida albicans
Correct answer: Staphylococcus aureus
Staphylococcus aureus is a gram-positive coccus that is a common part of the normal flora of the skin and nares. It is the leading cause of SSIs. Escherichia coli is a gram-negative rod primarily found in the gastrointestinal tract. Pseudomonas aeruginosa is a gram-negative rod often associated with hospital-acquired infections. Candida albicans is a fungus (yeast).
Question 3: A CSFA is assisting with an emergency exploratory laparotomy for a perforated duodenal ulcer with established peritonitis. How would this surgical wound be classified?
- Class I: Clean
- Class II: Clean-Contaminated
- Class III: Contaminated
- Class IV: Dirty/Infected (Correct answer)
Correct answer: Class IV: Dirty/Infected
A Class IV (Dirty/Infected) wound is one in which the organisms causing the postoperative infection were present in the operative field before the procedure. This includes old traumatic wounds with devitalized tissue and procedures involving existing clinical infection or perforated viscera. A perforated ulcer with established infection/peritonitis fits this definition. Class I is a clean, uninfected wound. Class II involves entering a hollow viscus under controlled conditions. Class III is a contaminated wound, such as one with gross spillage from the GI tract or a major break in sterile technique.
Question 4: During a procedure, the circulating nurse accidentally touches the sterile back table with their non-sterile scrubs. The contact was brief but definite. What is the most appropriate action?
- Place a sterile towel over the contaminated area.
- Ignore the contact as it was minor.
- Consider the entire sterile field contaminated and replace it. (Correct answer)
- Move sterile items away from the point of contact.
Correct answer: Consider the entire sterile field contaminated and replace it.
The principles of aseptic technique are absolute; if a non-sterile item touches a sterile field, the field is considered contaminated. The extent of microbial transfer is unknown, and simply covering the area or moving items away does not guarantee sterility. To ensure patient safety and prevent SSI, the entire field must be broken down and a new sterile field established.
Question 5: A biological indicator (BI) is used to verify the efficacy of a prevacuum steam sterilization cycle. Which spore-forming microorganism is the standard for this testing method?
- Bacillus atrophaeus
- Geobacillus stearothermophilus (Correct answer)
- Clostridium difficile
- Mycobacterium tuberculosis
Correct answer: Geobacillus stearothermophilus
Geobacillus stearothermophilus is a thermophilic bacterium whose spores are highly resistant to heat. This makes it the industry and FDA-recognized standard organism for validating the effectiveness of steam sterilization processes. Bacillus atrophaeus is used for ethylene oxide (EtO) and dry heat sterilization.
Question 6: To maximize effectiveness in preventing surgical site infections, when should the initial dose of a prophylactic intravenous antibiotic like cefazolin be administered?
- Within 2 hours after the surgical incision.
- As the final surgical dressing is being applied.
- Within 60 minutes prior to the surgical incision. (Correct answer)
- In the preoperative holding area, at least 3 hours before surgery.
Correct answer: Within 60 minutes prior to the surgical incision.
To be effective, prophylactic antibiotics must achieve adequate bactericidal concentrations in the serum and tissues by the time the incision is made. The Surgical Care Improvement Project (SCIP) guidelines and best practices recommend administering the first dose of most IV antibiotics within the 60-minute window before the surgical incision. For certain antibiotics with longer infusion times, like vancomycin, administration may begin within 120 minutes.
CSFA Microbiology and Infection Control Questions and Answers
A patient with suspected Creutzfeldt-Jakob disease (CJD) undergoes a brain biopsy.
According to CDC and WHO guidelines, which of the following is the most appropriate method for handling the involved surgical instruments?