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DISINFECTION
Although physical methods are often superior to chemical disinfection / sterilization, it is not practical to autoclave or subject many items to high heat, especially if the items can be damaged through repeated exposure to heat.
Instruments or materials, which cannot withstand sterilization in a steam autoclave or dry-air oven, can be sterilized with a gas such as ethylene oxide or broad-spectrum liquid chemical disinfectants.
Treatment of inert surfaces and heat labile materials can be accomplished through appropriate use of this disinfectants.
Selection of Disinfectants
Choice of a chemical disinfectant for use on contaminated equipment, supplies, laboratory surfaces or biohazardous waste depends upon a number of factors, including:
1) Type and level of microbial contamination
2) Concentration of active ingredient
3) Duration of contact between disinfectant and item to be disinfected
4) Presence of organic matter or soil load
5) Toxicity to individuals, culture systems, environment, residual toxicity on items,
6) PH, temperature, hardness of available dilution water,
7) Cost.
COMMON DISINFECTANTS
|
Disinfectant |
Effective Conc and Contact Times |
Advantages |
Disadv |
Examples of Laboratory Uses |
|
Alcohols |
• 70-80% ethanol • 60-95% isopropanol • 10-30 minutes |
• low toxicity • rapid action • low residue • non-corrosive |
• rapid evaporation limits contact time • flammable, eye irritant • may damage rubber, plastic, shellac • ineffective against bacterial spores |
• skin disinfectant (antiseptic) • surface decontamination • benchtop, cabinet wipedown |
|
Phenolic Compounds |
400-50,000 ppm (.05-1.5%) 10-30 minutes |
• tolerant of organic load, “hard” dilution water • leaves an active residue (may be desirable on some surfaces) • biodegradable |
• pungent odour, corrosive, some forms toxic • not sporicidal; limited activity against viruses • leaves a residual film (undesirable in culture systems) • may support growth of bacteria1 |
· instruments and equipment disinfection · disinfection of floors and other surfaces · antiseptic soaps and lotions |
|
Quaternary Ammonium Compounds |
• 500-15,000 ppm (.05-1.5%) • 10-30 minutes |
• combined detergent and germicidal activity • stable • working dilutions have low toxicity |
• Non-sporicidal, limited activity against viruses, mycobacteria • most formulations not readily biodegradable • may support growth of bacteria2 |
· surface decontamination · equipment wipedown · antiseptic formulations available · floors and walls |
|
Hydrogen Peroxide |
• 3-30% aqueous solution • 10-60 minutes • 6% for 30 minutes may kill spores |
• rapid action • no residue • low toxicity • environmentally safe |
• limited sporicidal activity • corrosive to some metals • potentially explosive at high concentrations • stock solutions irritating to skin and eyes |
· surface decontamination · instruments and equipment |