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Disinfection. Why Disinfect?. To reduce or eliminate exposure risk Biohazard waste disposal Spill cleanup Routine surface decontamination To eliminate contamination risk Preparation of microbiological media and supplies Preparation of work area for cleanliness-critical tasks.
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Why Disinfect? • To reduce or eliminate exposure risk • Biohazard waste disposal • Spill cleanup • Routine surface decontamination • To eliminate contamination risk • Preparation of microbiological media and supplies • Preparation of work area for cleanliness-critical tasks
Resistance to Disinfectants • Prions • Bacterial spores • Coccidia (Cryptosporidium) • Mycobacterium • Nonlipid viruses (Hep A, Polio) • Fungi • Rickettsiae, Chlamydiae • Vegetative bacteria • Lipid-containing viruses
Classes of Disinfectants • Chlorine • Iodine • Alcohol • Phenolics • Quaternary Ammonium • Glutaraldehyde • Hydrogen peroxide
Factors Influencing Efficacy • 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 • 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
Organic Load • Blood, sputum, milk, bedding, feed, manure • Proteins physically protect and stabilize many microorganisms • Adverse effect on action of many disinfectants
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 • 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 • Types of microbes present – spores, vegetative cells, viruses • Dried spills (from media, buffers) can protect microorganisms from contact with the disinfectant • pH • Age of the product/solution • Method of application (spray vs. wipe) • Rate of application • Storage condition