Factors Affecting the Efficacy of Disinfection and Sterilization

Factors Affecting The Sterilization Efficacy

Dr. Alaa gad MD,CIC

GDIPC,MOH CBAHI SURVYOR

DISINFECTION The

process of freeing an article or a surface from all or some of the living microorganisms but not necessarily bacterial spores

Sterilization The

process of freeing an article or a surface from all living microorganisms including viruses & bacterial spores

The activity of germicides against microorganisms depends on a number of factors, some of which are intrinsic qualities of the organism, others of which are the chemical and external physical environment.

Factors affecting DISINFECTION Conc

of disinfectant Time of action pH of the medium Temperature Nature & number of organisms Presence of extraneous material Others – hardness of water, relative humidity

Number of Microorganisms

 The

larger the number of microbes, the more time a germicide needs to destroy all of them. Spaulding illustrated this relation when he employed identical test conditions and demonstrated that it took 30 minutes to kill 10 B. atrophaeus (formerly Bacillus subtilis) spores but 3 hours to kill 100,000 Bacillus atrophaeusspores.  Reducing the number of microorganisms that must be inactivated through meticulous cleaning, increases the margin of safety when the germicide is used according to the labeling and shortens the exposure time required to kill the entire microbial load.

Location of Microorganisms Medical

instruments with multiple pieces must be disassembled and equipment such as endoscopes that have crevices, joints, and channels are more difficult to disinfect because penetration of the disinfectant of all parts of the equipment is difficult. Must be no air pockets and the equipment must be completely immersed for the entire exposure period.

Concentration and Potency of Disinfectants

With

other variables constant, and with one exception (iodophors), the more concentrated the disinfectant, the greater its efficacy and the shorter the time necessary to achieve microbial kill.

Temperature / PH  The

activity of most disinfectants increases as the temperature increases, too great an increase in temperature causes the disinfectant to degrade and weakens its germicidal activity and produce a potential health hazard.  An increase in pH improves the antimicrobial activity of some disinfectants (e.g., glutaraldehyde, quaternary ammonium compounds) but decreases the antimicrobial activity of others (e.g., phenols, hypochlorites, and iodine). The pH influences the antimicrobial activity by altering the disinfectant molecule or the cell surface .

Humidity / water hardness Relative

humidity is the single most important factor influencing the activity of gaseous disinfectants/sterilants. Water hardness reduces the rate of kill of certain disinfectants because divalent cations (e.g., magnesium, calcium) in the hard water interact with the disinfectant to form insoluble precipitates.

Factors Affecting The Sterilization Efficacy

1. Cleaning Failure

to adequately clean instrument results in higher bioburden, protein load, and salt concentration. These will decrease sterilization efficacy.

2. Bioburden The

natural bioburden of used surgical devices is 100 to 103 organisms(primarily vegetative bacteria), which is substantially below the 105-106 spores used with biological indicators.

3.Pathogen type Spore-forming

organisms are most resistant to sterilization and are the test organisms required for FDA clearance. However, the contaminating microflora on used surgical instruments consists mainly of vegetative bacteria.

4. Protein Residual

protein decreases efficacy of sterilization. However, cleaning appears to rapidly remove protein load.

5.Salt Residual

salt decreases efficacy of sterilization more than does protein load. However, cleaning appears to rapidly remove salt load.

6. Biofilm accumulation 

Biofilms are microbial communities that are tightly attached to surfaces and cannot be easily removed.



Bacteria within biofilms are up to 1,000 times more resistant to antimicrobials than are the same bacteria in suspension .



Chlorine and monochloramines can effectively inactivate biofilm bacteria .



Biofilms have been found in whirlpools, dental unit waterlines, and numerous medical devices (e.g., contact lenses, pacemakers, hemodialysis systems, urinary catheters, central venous catheters, endoscopes)



Some enzymes and detergents can degrade biofilms or reduce numbers of viable bacteria within a biofilm, but no products are EPA-registered or FDAcleared for this purpose.

7. Lumen length Increasing

lumen length impairs sterilant penetration. May require forced flow through lumen to achieve sterilization.

8. Lumen diameter Decreasing

lumen diameter impairs sterilant penetration. May require forced flow through lumen to achieve sterilization.

9. Restricted flow Sterilant

must come into contact with microorganisms. Device designs that prevent or inhibit this contact (e.g., sharp bends, blind lumens) will decrease sterilization efficacy.

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.

Thank you