Biological Indicators are typically bacterial spores in a growth medium or inoculated to a spore or paper strip, which are put through the sterilization cycle intended for the drug or medical device, recovered and then checked for survivors.
Bacillus stearothermophilus: used to verify steam sterilization cycles.
Bacillus atrophaeus: used to verify peroxide sterilization cycles.
Bacillus pumilus: used to verify gamma irradiation cycles..
Incubation conditions will depend upon the organism and the manufacturer’s use instruction. A typical incubation for Bacillus stearothermophilus is 2 days at 55 – 60°C.
The Certificate of Analysis (COA) will indicate the number of spores on a Biological Indicator. The number is important in verifying the Sterility Assurance Level (SAL) of the validated process. FOCUS can confirm the spore count via validated methodologies.
- Time Kill
The Certificate of Analysis (COA) will also indicate the D-value of the Biological Indicator. D-value is the time required to reduce the population by one log. Determining D-value requires specialized equipment such as a Bier Vessel.
An alternative to confirming the D-value is to determine the minimum expected survival and maximum expected kill time.
The minimum expected survival time = (Not Less than D Value) x (Log viable spores -2)
The maximum expected kill time = (Not more than D Value) x (Log viable spores +4)
FOCUS can verify these values.