Sterilization

The only way to ensure that sterilization has occurred is to use the biological monitoring methods. This is because these are the only tests done which show whether or not actual microbial life has been killed. Biological methods are the only ones which are recommended by the CDC (Centers for Disease Control and Prevention), the AAMI (Association for the Advancement of Medical Instrumentation), the AMA (American Medical Association), OSHA, and OSAP (Office Safety and Asepsis Procedures Foundation)

Biological monitoring is basically evaluating a sterilization process by rendering highly resistant bacterial spores biologically inert. The highly resistant bacterial spores used varies depending on what kind of sterilizer was used. For example Bacillus stearothermophilus spores for steam and chemical vapor sterilizers, Bacillus subtilis spores for dry heat and ethylene oxide sterilizers. These specific Bacillus spores are used because they are more resistant, and present in greater numbers than are the common microbial contaminants found on patient care equipment. If it is proven that these spores have been killed, it is strongly implied that other potential pathogens in the load have also been killed.

In this method, living spores which are resistant to whichever sterilizing agent is being tested are prepared in either a self contained system, such as dry spore strips, or in sealed vials or ampules of spores in suspension. Then the prepared living spores are exposed to the sterilant. After exposure they are incubated along with an unexposed or control group of spores for the same period of time. If sterilization has occurred the spores which were exposed will not multiply. The control group should grow microorganisms and display a change in color. If this does not occur, then it's spores have been inactivated and the test is invalid. This is because if the control spores were inactivated, it is possible the spores which were exposed also became inactivated prior to sterilization. Every item sterilized in the load with the indicator involved in an invalid test is considered unsterile. This is the case whenever there is an uncertainty about either the indicator of the control.

Biological testing should be done often. The CDC recommends one spore strip test per sterilizer per week. The biological indicator should be placed