Disinfection

Why Disinfect? To reduce or eliminate exposure risk To reduce or eliminate exposure risk  Biohazard waste disposal  Spill cleanup  Routine surface decontamination To eliminate contamination risk To eliminate contamination risk  Preparation of microbiological media and supplies  Preparation of work area for cleanliness-critical tasks

Resistance to Disinfectants Prions Prions Bacterial spores Bacterial spores Coccidia (Cryptosporidium) Coccidia (Cryptosporidium) Mycobacterium Mycobacterium Nonlipid viruses (Hep A, Polio) Nonlipid viruses (Hep A, Polio) Fungi Fungi Rickettsiae, Chlamydiae Rickettsiae, Chlamydiae Vegetative bacteria Vegetative bacteria Lipid-containing viruses Lipid-containing viruses

Classes of Disinfectants Chlorine Chlorine Iodine Iodine Alcohol Alcohol Phenolics Phenolics Quaternary Ammonium Quaternary Ammonium Glutaraldehyde Glutaraldehyde Hydrogen peroxide Hydrogen peroxide

Factors Influencing Efficacy Surface/Topography – uneven, cracked or pitted surfaces especially wooden surfaces can hide microorganisms and are difficult to disinfect Surface/Topography – uneven, cracked or pitted surfaces especially wooden surfaces can hide microorganisms and are difficult to disinfect Temperature - elevated temperatures may enhance germicidal action but also evaporation rate Temperature - elevated temperatures may enhance germicidal action but also evaporation rate Relative Humidity – many disinfectants have optimal relative humidity range for maximum effectiveness Relative Humidity – many disinfectants have optimal relative humidity range for maximum effectiveness Water Hardness – some disinfectants may be less effective when diluted in hard water Water Hardness – some disinfectants may be less effective when diluted in hard water

Organic Load Organic Load  Blood, sputum, milk, bedding, feed, manure  Proteins physically protect and stabilize many microorganisms  Adverse effect on action of many disinfectants

Concentration Concentration  In most cases, the higher the concentration, the more rapid the kill  Consider potential damage to surfaces or tissues  Reducing concentration to avoid damage will require additional contact time  Ultimately, disinfectant will no longer be active enough to be useful

Contact Time Contact Time  Disinfectants should be effective with a short contact time  Manufacturer’s recommended contact time may be unrealistic under in-use condition  Contact time may depend on the method of application  For surface applications, loss by evaporation may require frequent applications to achieve contact time

Some Other Factors Dirt, grease and oils – all can protect the organism and will repel water based disinfectants Dirt, grease and oils – all can protect the organism and will repel water based disinfectants Types of microbes present – spores, vegetative cells, viruses Types of microbes present – spores, vegetative cells, viruses Dried spills (from media, buffers) can protect microorganisms from contact with the disinfectant Dried spills (from media, buffers) can protect 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 condition Storage condition