A hospital microbiology laboratory needs to validate the efficacy of a new steam sterilizer before it is put into routine use. Which investigation is the most appropriate choice to confirm that the sterilizer achieves adequate penetration and sterilization of wrapped instruments?

Question

Accepted Answer

B. Biological indicator using Geobacillus stearothermophilus spores. ## Validation of Steam Sterilization

**Key Point:** Biological indicators (BIs) are the gold standard for validating sterilizer efficacy because they directly test the sterilizer's ability to kill highly resistant bacterial spores under the actual conditions of use.

### Why Biological Indicators?

Biological indicators contain spores of *Geobacillus stearothermophilus* (formerly *Bacillus stearothermophilus*), which are:
- The most heat-resistant non-pathogenic spores
- Naturally killed by steam sterilization at 121°C for 15–30 minutes
- Placed inside wrapped bundles to test penetration into the most challenging locations

After sterilization, the BI is incubated to check for any surviving spores. A negative culture (no growth) confirms sterilization efficacy.

### Comparison of Validation Methods

| Method | Purpose | Limitation |
|--------|---------|------------|
| **Biological Indicator** | Confirms actual killing of spores | Gold standard; takes 24–48 hrs for culture results |
| Chemical Indicator | Visual confirmation of exposure to heat/steam | Does NOT confirm sterilization; only shows exposure |
| Temperature Monitoring | Confirms temperature reached | Does NOT confirm penetration or adequate exposure time |
| Visual Inspection | Detects gross equipment failure | Subjective; does not validate sterilization |

**High-Yield:** Biological indicators are mandatory for:
- Initial validation of new sterilizers
- Periodic monitoring (at least weekly)
- After any equipment repair or maintenance

**Clinical Pearl:** Chemical indicators are used for routine monitoring of each load (faster feedback), but BIs are the definitive proof of sterilizer function.

**Warning:** A positive BI (spore growth) indicates sterilizer failure and the device must be taken out of service immediately until repaired.

[cite:Park 26e Ch 3]

Answer

A. Chemical indicator strips placed on the surface of instruments

Answer

C. Visual inspection of the autoclave chamber for condensation

Answer

D. Temperature monitoring with a mercury thermometer inside the chamber

A hospital microbiology laboratory needs to validate the efficacy of a new steam sterilizer before it is put into routine use. Which investigation is the most appropriate choice to confirm that the sterilizer achieves adequate penetration and sterilization of wrapped instruments?

Explanation

Practice similar questions