Sterilization and factors affecting its efficacy

 Factors affecting Sterilization and its Efficacy


Based on risk adjusted classification of hospital instrument for the probability of transmitting infections Spaulding classification  we do sterilization for the critical items (that touches sterile body cavity e.g. surgical instruments) which is the a process that destroys or eliminates all forms of microbial life and is carried out in health-care facilities by physical or chemical methods to prevent disease transmission associated with the use of that item . Many methods are used for sterilizing instruments inside any health care facility e.g. Steam under high pressure, dry heat, and low temp sterilization EtO gas,  gas plasma, and liquid chemicals (which are called chemical sterilants that can be used as high level disinfectant if used for shorter exposure time) all of them have the ability to kill all pathogen if the proper procedure was implemented for reprocessing the reused items , so the sterilization is the ability to kill all living pathogen including bacterial spores which differ from disinfection that lack the ability to kill the microbial spores and are used for disinfecting non critical items and semi critical items based on Spaulding classification (the semi critical items that touches the mucus membranes can be disinfected or sterilized based on the use and the manufacturer recommendation mainly by using chemical sterilants )

 Factors affecting Sterilization and its Efficacy

Factors affecting Sterilization and its Efficacy


Because most medical and surgical devices used in healthcare facilities are made of materials that are heat stable e.g. stainless steel that used for surgical intervention so it can be sterilized used heat e.g. autoclave but now a days there has been an increase in medical devices and instruments made of materials (e.g., plastics) that could not be sterilized under high temperature and the manufacturer claim those are reusable instruments so for reprocessing those items we have to use low-temperature sterilization e.g. Ethylene oxide, hydrogen peroxide gas plasma, peracetic acid immersion, ozone) they are being used to sterilize medical devices.


Inadequate sterilization can lead to high probability for pathogen transmission (rarely documented due to the wide margin of safety associated with sterilization process) caution is needed to follow the right procedure. The “sterile” is measured as a probability of sterility for each item to be sterilized. This possibility can be referred to as the sterility assurance level (SAL) of the product which is the probability of a single viable microorganism occurring on a product after sterilization which is the lethality of the entire sterilization process. SAL is normally expressed a 10n.

To make sure of the efficacy of the sterilization process we need to follow the reprocessing of reusable items and implement a quality assurance (challenge tests) for the process in order to get safe instrument to be handled by health care providers to be used for the patients the following factors can affect the sterilization efficiency:


  1. Cleaning :   inadequate cleaning of the instruments before sterilizing will lead to higher bio burden , protein load and salt concentration that will decrease the sterilization efficacy so it is always called proper clean first then perform sterilization
  2. Bioburden :Natural bioburden for the reused surgical devices is almost 100 organisms that are primarly vegetative bacterial which is still below the spore load 106 in the challenge test of biological indicator (Spore test )
  3. Pathogen type : the most difficult organism are the spore forming organism e.g. Clostridium difficile , those organism resistant to sterilization so we are using them as the challenge test to check the sterilization cycle was effective and kill all pathogen or we have failure.
  4. Protein :residual protein will decrease the efficacy of sterilization in general if not clean that is mean not sterile but protein is easily removed by using effective enzymatic detergent
  5. Salt:  same like protein residual salt decrease the efficacy of sterilization even more decrease than protein but cleaning is the key to remove both
  6. Biofilm :Biofilm accumulation reduce the sterilization efficacy by impairing the exposure of the steriliant to the microbial cell (mainly the chemical steriliant )
  7. 7.       Lumen length: as the instrument has lumen so penetration of sterilant inside the lumen is needed and if the lumen increase in length so it need to more force flow of the sterilant to achieve sterilization all sterilizers manufacturers’ have study about the length of the instruments that their sterilizer can penetrate
  8. 8.       Lumen diameter: once the instrument lumen is very narrow so penetration will be difficult and also all sterilizer’s manufacturers’ have study about the diameter of the instruments that their sterilizer can penetrate.
  9. 9.       Restricted flow: Sterilant must come into contact with microorganisms. the designs of the device can prevent or inhibit this contact (e.g., sharp bends, blind lumens) will decrease sterilization efficacy.
  10. 10.    Device design and construction: Materials used in construction may affect compatibility with different sterilization processes and affect sterilization efficacy. Design issues (e.g., screws, hinges) will also affect sterilization efficacy.




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