Disinfection

Why Disinfect?Why Disinfect?

To reduce or eliminate exposure risk To reduce or eliminate exposure risk Biohazard waste disposal Biohazard waste disposal Spill cleanup Spill cleanup Routine surface decontamination Routine surface decontamination

To eliminate contamination risk To eliminate contamination risk Preparation of microbiological media and Preparation of microbiological media and

supplies supplies Preparation of work area for cleanliness-critical Preparation of work area for cleanliness-critical

taskstasks

Resistance to DisinfectantsResistance to Disinfectants

Prions Prions Bacterial spores Bacterial spores Coccidia Coccidia

((CryptosporidiumCryptosporidium) ) Mycobacterium Mycobacterium Nonlipid viruses (Hep A, Nonlipid viruses (Hep A,

Polio) Polio) Fungi Fungi Rickettsiae, Chlamydiae Rickettsiae, Chlamydiae Vegetative bacteria Vegetative bacteria Lipid-containing viruses Lipid-containing viruses

Classes of DisinfectantsClasses of Disinfectants

Chlorine Chlorine Iodine Iodine Alcohol Alcohol Phenolics Phenolics Quaternary Ammonium Quaternary Ammonium Glutaraldehyde Glutaraldehyde Hydrogen peroxideHydrogen peroxide

Factors Influencing EfficacyFactors Influencing Efficacy

Surface/TopographySurface/Topography – uneven, cracked or pitted – uneven, cracked or pitted surfaces especially wooden surfaces can hide surfaces especially wooden surfaces can hide microorganisms and are difficult to disinfect microorganisms and are difficult to disinfect

Temperature - Temperature - elevated temperatures may elevated temperatures may enhance germicidal action but also evaporation rate enhance germicidal action but also evaporation rate

Relative Humidity – Relative Humidity – many disinfectants have many disinfectants have optimal relative humidity range for maximum optimal relative humidity range for maximum effectiveness effectiveness

Water Hardness – Water Hardness – some disinfectants may be less some disinfectants may be less effective when diluted in hard watereffective when diluted in hard water

Organic Load Organic Load Blood, sputum, milk, bedding, feed, Blood, sputum, milk, bedding, feed,

manure manure Proteins physically protect and stabilize Proteins physically protect and stabilize

many microorganisms many microorganisms Adverse effect on action of many Adverse effect on action of many

disinfectants disinfectants

Concentration Concentration In most cases, the higher the In most cases, the higher the

concentration, the more rapid the kill concentration, the more rapid the kill Consider potential damage to surfaces or Consider potential damage to surfaces or

tissues tissues Reducing concentration to avoid Reducing concentration to avoid

damage will require additional contact damage will require additional contact time time

Ultimately, disinfectant will no longer Ultimately, disinfectant will no longer be active enough to be useful be active enough to be useful

Contact Time Contact Time Disinfectants should be effective with a Disinfectants should be effective with a

short contact time short contact time Manufacturer’s recommended contact Manufacturer’s recommended contact

time may be unrealistic under in-use time may be unrealistic under in-use condition condition

Contact time may depend on the method Contact time may depend on the method of applicationof application

For surface applications, loss by For surface applications, loss by evaporation may require frequent evaporation may require frequent applications to achieve contact timeapplications to achieve contact time

Some Other FactorsSome Other Factors Dirt, grease and oils – all can protect the organism Dirt, grease and oils – all can protect the organism

and will repel water based disinfectants and will repel water based disinfectants Types of microbes present – spores, vegetative Types of microbes present – spores, vegetative

cells, viruses cells, viruses Dried spills (from media, buffers) can protect Dried spills (from media, buffers) can protect

microorganisms from contact with the disinfectant microorganisms from contact with the disinfectant pH pH Age of the product/solution Age of the product/solution Method of application (spray vs. wipe)Method of application (spray vs. wipe) Rate of application Rate of application Storage conditionStorage condition