Disinfection

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Disinfection
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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

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Resistance to Disinfectants

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

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Classes of Disinfectants

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

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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

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

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• 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

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• Contact Time
• Disinfectants should be effective with a short
  contact time
• Manufacturers 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

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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