By Adrianne Jerrett Updated Mar 24, 2022
Sterilization is the only process that guarantees the complete elimination of all microorganisms on equipment or materials. In healthcare, it stops disease transmission between patients; in food production it prevents food‑borne illnesses; and in research labs it eliminates cross‑contamination between samples.
While both aim to kill microbes, disinfection only destroys most organisms and leaves highly resistant spores intact. Sterilization, on the other hand, must eradicate every single microorganism, including spores.
Bacterial spores form when environmental conditions become hostile, safeguarding the bacterium’s DNA until conditions improve. Three protective layers—spore wall, cortex, and outer coat—shield the DNA, and some spores possess heat‑resistant enzymes such as catalase, enabling them to survive for years.
Heat‑based methods, especially steam sterilization via autoclaves, dominate because they are effective and safer than toxic chemicals like glutaraldehyde. Steam sterilizers operate at temperatures above 250 °F (121 °C) to guarantee complete microorganism kill.
Autoclaves expel air from the chamber and introduce hot steam, heating contents to about 270 °F (132 °C) for roughly 20 minutes. The high pressure, coupled with the device’s robust design, ensures thorough sterilization.
Each week, run a spore test to confirm that your autoclave is functioning correctly. Spore tests contain nonpathogenic bacterial spores—typically Geobacillus stearothermophilus—either in a vial or on a filter paper strip. Follow the manufacturer’s instructions closely.
Place the test kit in the autoclave alongside regular loads and run a standard cycle. Rotate the position of the test kits in successive runs to identify any cold spots or under‑treated areas.
After the cycle, send the test kit to a certified lab or incubate it on-site. If bacterial growth is detected, the sterilization failed.
A negative result (no growth) does not prove absolute success, but a positive result unequivocally indicates a problem. Causes may include mechanical faults, overloading, incorrect settings, or cycle interruptions. If a positive result occurs, switch to an alternative sterilization method until the issue is resolved.
