Method Of Evaluating The Effectiveness Of A Sterilization Process

Abstract

A method is provided for establishing resistance characteristics of a biological indicator in a sterilization process using a sterilant vapor. The method includes the step of creating a biological indicator inactivation profile by obtaining differential sterilant vapor pressure values in a sterilization chamber during sterilant vapor injection and determining D-values as a function of the differential sterilant vapor pressure values obtained. The biological indicator inactivation profile, when represented as a function of differential sterilant vapor pressure, may be linear over the full range of inactivation. The biological indicator inactivation profile may be created by injecting the sterilant vapor into the sterilization chamber and measuring biological indicator survival at different differential sterilant vapor pressure values. The method may include providing biological indicator inactivation data during sterilization at a given sterilization chamber temperature and initial sterilant concentration for use in creating the biological indicator inactivation profile at another temperature and sterilant concentration.

1 - 17 . (canceled) 
     
     
         18 . A method for evaluating the effectiveness of a sterilization process, the method comprising:
 effecting the sterilization process using a biological indicator and sterilant vapor in a sterilization chamber;   measuring biological indicator survival at different differential sterilant vapor pressures; and   evaluating the measured biological indicator survival against a biological indicator inactivation profile for evaluating the effectiveness of the sterilization process;   wherein the biological indicator inactivation profile expresses D-values as a function of differential sterilant vapor pressure.   
     
     
         19 . The method of  claim 18 , further comprising creating the biological indicator inactivation profile by gradually injecting sterilant vapor into the sterilization chamber and measuring biological indicator survival at different differential sterilant vapor pressures determined at different times of the sterilant vapor injection. 
     
     
         20 . The method of  claim 19 , wherein the gradually injecting includes pulsed injection of the sterilant vapor for the generation of a layer of micro-condensation of the sterilant in the chamber. 
     
     
         21 . The method of  claim 18 , wherein creating a biological indicator inactivation profile further includes obtaining a temperature in the sterilization chamber during sterilant vapor injection and calculating biological indicator inactivation data during sterilization at a given sterilization chamber temperature and initial sterilant concentration, for use in creating the biological indicator inactivation profile for another sterilization chamber temperature and sterilant concentration. 
     
     
         22 . The method of  claim 20 , wherein creating a biological indicator inactivation profile further includes obtaining a temperature in the sterilization chamber during sterilant vapor injection and calculating biological indicator inactivation data during sterilization at a given sterilization chamber temperature and initial sterilant concentration, for use in creating the biological indicator inactivation profile for another sterilization chamber temperature and sterilant concentration. 
     
     
         23 . The method of  claim 18 , further comprising evaluating the biological indicator inactivation profile against a standard to evaluate the effectiveness of the biological indicator in testing a sterilization process. 
     
     
         24 . The method of  claim 23 , wherein the sterilant vapor is hydrogen peroxide vapor. 
     
     
         25 . The method of  claim 18 , wherein the sterilant vapor is hydrogen peroxide vapor. 
     
     
         26 . A method for establishing resistance characteristics of a biological indicator in a sterilization process using a sterilant vapor, the method comprising:
 a) exposing a biological indicator by injecting sterilant vapor into a sterilization chamber,   b) obtaining differential sterilant vapor pressure values occurring during sterilant vapor injection into the sterilization chamber, and   c) repeating steps a) and b) one or more times to obtain one or more exposed biological indicators, wherein the sterilant vapor pressure is different for each exposure, and   measuring a number of surviving microorganisms in each of the exposed one or more biological indicators as a function of the differential sterilant vapor pressure values to create a biological indicator inactivation profile for establishing the resistance characteristics of the biological indicator.   
     
     
         27 . The method of  claim 26 , wherein the biological indicator inactivation profile is created by gradually injecting the sterilant vapor into the sterilization chamber and measuring biological indicator survival at different differential sterilant vapor pressures determined at different times of the sterilant vapor injection. 
     
     
         28 . The method of  claim 27 , wherein the gradually injecting includes pulsed injection of the sterilant vapor for the generation of a layer of micro-condensation of the sterilant in the chamber. 
     
     
         29 . The method of  claim 26 , further comprising obtaining a temperature in the sterilization chamber during sterilant vapor injection and calculating biological indicator inactivation data during sterilization at a given sterilization chamber temperature and initial sterilant concentration, for use in creating the biological indicator inactivation profile for another sterilization chamber temperature and sterilant concentration. 
     
     
         30 . The method of  claim 28 , further comprising obtaining a temperature in the sterilization chamber during sterilant vapor injection and calculating biological indicator inactivation data during sterilization at a given sterilization chamber temperature and initial sterilant concentration, for use in creating the biological indicator inactivation profile for another sterilization chamber temperature and sterilant concentration. 
     
     
         31 . The method of  claim 26 , further comprising evaluating the biological indicator inactivation profile against a standard to evaluate the effectiveness of the biological indicator in testing a sterilization process. 
     
     
         32 . The method of  claim 31 , wherein the sterilant vapor is hydrogen peroxide vapor.