Infection prevention with germicides

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If you've ever worked in a veterinary setting or animal shelter, you know that there are tons of different kinds of cleaners used for different things. Why don't we just bleach everything? Why do we have to let some disinfectants sit for 10 minutes before wiping down the area? This article is a summary of a great lecture we had at my veterinary school about infection prevention and control in the veterinary hospital.

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Disinfectants and antiseptics both fall under the category of germicides. The difference is that disinfectants are used for killing microbes on non-living surfaces, while antiseptics are used on skin and other living tissues. It is important to note that disinfection and antiseptics do NOT necessarily sterilize an area. Sterilization is the complete elimination of microbes, which can be achieved through autoclaving, ethylene oxide gassing, and dry heat. Disinfectants and antiseptics do not necessarily achieve a 100% removal of microbes.
The chemical structure, concentration, contact duration with the surface or tissue, and presence of organic matter all affect the efficacy of your cleaning substance. Especially, make sure to pay attention to concentration and contact time. Just adding "a splash" of Accel to a bucket of mop water does NOT cut it!

DISINFECTANTS (use for surfaces, not skin)

• QUATs (quaternary ammoniums; e.g. Vindicator, LemonQUAT) are lower level disinfectants and do not kill bacterial spores. Some bacteria can actually grow in quats! These are best for cleaning counters and floors.
  
• Bleach (sodium hypochlorite) inactivates parvovirus, one of the most resistant viruses known! This can be achieved using a 1:32 dilution (1 part bleach, 32 parts water). Stronger dilutions (1:10) can kill bacterial spores, but can also be corrosive.
• Accelerated H2O2 (Accel) can actually achieve sterilization if you let it sit for 10 minutes at a 4.5% dilution. It can inactivate non-enveloped viruses (environmentally hardy viruses) at a 1:16 dilution and a 5 minute contact time. You can even get Accel in wipe form for using to disinfect your stethoscope!
  
• Potassium peroxymonosulfate (Trifectant, Vikron S) can inactivate non-enveloped viruses at a solution of 1%, but is expensive! Use for special areas like the ICU, operating room, quarantine, and isolation ward.
• Glutaraldehyde (Cidex) can disinfect surfaces after 20 minutes of contact time, but can achieve sterility after 10 hours. It is good for sterilizing instruments that are too delicate or too large to be autoclaved, like endoscopes and some dental equipment. It can be irritating to tissues, so wear gloves!
• Ortho-phthaldehyde- similar to glutaraldehyde in utility but stains skin gray. Use gloves!
• Check out this document for more information on disinfectants for infection prevention.

ANTISEPTICS (use for skin and instruments)

• Alcohol (isopropyl alcohol/isopropanol/IPA and ethyl alcohol/ethanol/EtOH) can rapidly destroy enveloped viruses (but not non-enveloped viruses) and bacteria, but it does not kill bacterial spores and can be irritating on mucous membranes. A 60-90% solution is optimal. Foams and gels are useful for cleaning your hands throughout the day, but can be drying-- chapped hands means there is a better chance bacteria can penetrate your skin, so make sure to moisturize too.  
• Chlorhexidine (Nolvasan) comes in 4% scrub (soapy) and 2% solution formulations. The scrub removes dirt and oil. It is non-irritating and provides provides up to two days of antiseptic properties as it binds to skin keratin.  It is great for prepping catheter sites and surgical incision sites. It stings more than betadine when applied to open wounds, however.
  
• Betadine (povidone-iodine) is a dark orange-brown liquid that is also available as a scrub and a solution preparation. It stains skin orange-brown too. It has a residual activity of around 5 hours, so more frequent application is required compared to chlorhexidine for long term care of a wound site. However, it stings less than chlorhex does on fresh tissue.
  
• Check out this document for more information on antiseptics.