Sterilants and Disinfectants: A Primer

[BuckarooBanzai]

If you choose to avail yourself of any of these compounds, please take the time to download/read the appropriate MSDS (Materials Safety Data Sheets). Many of these chemicals can destroy your eyes/lungs and some of them can give you cancer. Follow all manufacturer’s directions for exposure and use! Get your cancer from cigarettes…like me…

Do not EVER mix any of these agents! Peracetic acid will heat and could explode if mixed with alcohol. Bleach mixed with any basic/acidic compound will evolve chlorine gas. Ethylene oxide can react violently with water (and explode). Read the MSDS and follow it to the letter. Do NOT bet your health/safety on this post!

None of this is conjecture. It is all based on existing publications and personal experience, though I have tried to keep the “commentary” to a minimum. If you spot any glaring errors, PLEASE let me know! Disinformation is not my business…

Basic sterile procedure for instruments:
1> Wash the item thoroughly with disinfectant soap/detergent and the hottest water you can stand to have your hands in. Dishwashers are far superior to hand washing in this respect.
2> Rinse the item thoroughly with the hottest water you can stand. Most of the chemicals listed below will not perform as expected in the presence of organic matter (like dirt or soap residue).
3> If using a pressure cooker, immediately wrap the item in aluminum foil to avoid any dust/dirt contamination. If using chemicals, immerse the item immediately after it is dry (water can have adverse effects on some chemicals –some will simply be diluted while others may give off toxic/explosive gasses).
4> Pressure or chemical sterilize immediately after cleaning.
5> Keep the item in the pressure cooker/autoclave until you are ready to use it.
6> Don’t un-wrap the item until you are inside the sterile field.
7> Don’t sterilize days/weeks before the instrument is used.


Sterilants:
Sterilizing is the process of destroying ALL microorganisms, bacteria, germs and spores. Any sterilizing agent, chemical or manual, is called a Sterilant. Chemical sterilants are effective based on exposure (generally immersion) for set periods of time under specific conditions. As an example, unwrapped (clean) instruments are sterilized by immersion in 2.5% glutaraldehyde after 10 hours at 22C. The same instruments are sterilized by wet autoclave after 15 minutes of 15psi steam (15psi steam is 121C). Sterilization procedures are based on exhaustive tests against a wide range of contaminants under a variety of conditions and can be reproduced quite reliably if you simply follow directions.

Common chemical sterilants: glutaraldehyde, peracetic acid, ortho-phthalaldehyde
Uncommon (dangerous) chemical sterilants: ethylene oxide gas
Manual sterilants: autoclaves/pressure cookers, gamma radiation

Commercial glutaraldehyde sterilants:
MetriCide 2.6%
Rapicide 2.5%
Cidex 2.4%
Cidex Plus 3.4%

What’s good about glutaraldehyde:
It is cheap and easily available, having been mass produced for 30+ years. It is the most commonly used chemical sterilant. It is non corrosive on clean surfaces. It will not fog glass/optics or plastics. A sufficient soak in room temperature glutaraldehyde will kill virtually anything/everything. It is highly effective in the presence of organic material (works well even on a dirty surface). It is equally effective in cold, hot, hard or soft water. After it’s active period ends, it can be disposed of right down the drain in most states (you must chemically deactivate before disposing in California). Glutaraldehyde can be immediatly deactivated by the addition of glycine or sodium bisulfate (these are sold to clean up glutaraldehyde spills).

What’s bad about glutaraldehyde:
There aren’t many of them, but glutaraldehyde resistant bugs do exist. It has a very strong smell that can linger for days (the smell is highly reminiscent of formaldehyde). It must be used with extremely good ventilation. It will penetrate latex in 10-15 minutes (use nitrile gloves). Prolonged exposure to it will cause you to sensitize (it gets more irritating with every exposure). You must mix a dry powder with it to activate – it will then deactive some time later (usually 12-30 days, check your label). It is highly toxic. It is carcinogenic. If not inactivated before disposal, it is a hazardous waste in California. Glutaraldehydes are banned as sterilants in the U.K. because of safety concerns.

Commercial peracetic acid sterilants:
Acecide 7.0% (not available in US…yet…)
Antec HyperOx: 5%
Steris Spor-Klenz 4.5%
Asperix 5%
Asperix Ultra 10%
OxyStrong 1%, 5%, 15%
Steris Sporgon .23%
EndoSpor .23%
Perasafe powder (concentration based on mix ratio)
Virkon powder (concentration based on mix ratio)

What’s good about peracetic acid:
Low smell (vinegar) and no fumes. Decomposes into oxygen, water and acetic acid. Peracetic acid is basically a highly concentrated solution of hydrogen peroxide. Available in powder form that lets you set your own concentration levels. Not a sensitizer. Not carcinogenic. Non corrosive and will not fog optics. Extreme ventilation is not required to maintain an OSHA compliant work space.

What’s bad about peracetic acid:
Expensive. Solutions have a short shelf life. It is a highly efficient oxidizer and should NOT be used with alcohols at high concentration (spontaneous combustion risk). It is an irritant. Concentrated peracetic acid compounds are explosive above 110C. Pure peracetic acid can explode if treated roughly. It is far less efficient on dirty surfaces/tools.

Commercial ortho-phthalaldehyde sterilants:
Cidex OPA, 0.55%

What’s good about ortho-phthalaldehyde:
Very low smell. Non sensitizer. Non irritant. Even more effective than glutaraldehyde (there are no known ortho-phthalaldehyde resistant bugs). Does not require mixing to activate. Does not require extreme ventilation.

What’s bad about ortho-phthalaldehyde:
Expensive. It eats through latex gloves (use nitrile). It is pretty new to the market and long term risk studies are minimal. If not inactivated before disposal, it is a hazardous waste in California.

Ethylene oxide gas:
Find your own trade names if you think you want to mess with this stuff. I include it only as a reference, not a suggested process.

What’s good about ethylene oxide:
It is the most effective chemical sterilant known to man. It does not cloud glass or plastic. It works well at low temperature. It is arguably more effective than gamma radiation at destroying microbial life. There are no known ethylene oxide resistant microorganisms or spores. Ethylene oxide kills everything.

What’s bad about ethylene oxide:
It is HIGHLY toxic. It is one of the most toxic substances on earth. It is highly flammable/explosive. It evolves explosive gasses on contact with water. To use it safely, you need a very expensive machine and ventilator. It is colorless and only has a mild smell of ether even at toxic concentrations. Ethylene oxide liquid will accumulate static charge when jostled (shaking it up can cause it to spontaneously spark and explode). It is highly carcinogenic and mutagenic. Acceptable employee exposure levels are less than 1ppm over an 8 hour assay.


Disinfectant:
Any agent or process that kills most living organisms, bacteria and germs is a disinfectant. Unlike sterilization, disinfection is an open ended term with more than one level of contaminant destruction qualifying (high level disinfection is one step away from sterilization, low level disinfection can be achieved with soap and water). Virtually any agent which inhibits disease causing microorganisms is called a disinfectant. Disinfectants do NOT kill mycobacteria and most spores (psilocybe spores ARE killed by most disinfectants – Clostridia is a “common” spore unaffected by disinfectants). Disinfectants do not destroy all contaminants; they reduce them to an “acceptable” level. All sterilants are effective disinfectants. Disinfectants can not be used as sterilants.

Common chemical disinfectants: hypochlorites (halogens), phenolics, alcohols, iodines and quaternary ammoniums


Commercial sources of hypochlorites disinfectants:
Bleach
Presept
Purex
Milton

What’s good about hypochlorites:
Cheap and available from the grocery store. Wide range of activity (concentration dependent) on bacteria, fungi, viruses and spores. Great deodorizer. Long history of product safety with a noted lack of side effects. Hippie has demonstrated that low concentrations of hypochlorites do not kill mycelium.

What’s bad about hypochlorites:
Highly corrosive. Irritants. Long term exposure is very bad for the respiratory system. Not effective against bacterial spores or mycobacteria. Highly ineffective unless the surface/tool is clean (inactivated by organic matter). Decays spontaneously with time or exposure to light – diluted bleach solutions loose most of their activity within 24-36 hours. Can evolve chlorine gas if heated or mixed with a basic/acidic compound.


Commercial sources of phenolic disinfectants:
Lysol
Straphene
O-Syl
Matar
Stercol
Hycolin

What’s good about phenolics:
Cheap and readily available. Very effective against fungi, bacteria and some viruses.

What’s bad about phenolics:
Very limited activity against some viruses and spores. Irritant (and it stinks). VERY HIGH TOXICITY TO CATS, REPTILES AND BIRDS. Can cloud/soften some plastics. Some phenolic disinfectants leave a greasy residue.


Alcohols:
Methanol
Ethanol
Isopropanol

What’s good about alcohols:
Cheap and available from the drug store. Good activity against bacteria. Non irritating.

What’s bad about alcohols:
Limited activity against viruses and fungi. Very limited activity on dirty surfaces/tools. Clouds some plastics. Makes acrylics very brittle (DON’T soak your acrylic water pipe in alcohol). Highly flammable as a liquid and explosive as an aerosol.


Commercial sources of iodine disinfectants:
Betadyne
Povadone
Wescodyne
Prepodyne

What’s good about iodines:
Readily available. Active against a wide range of bacteria, fungi, viruses and most micro-organisms. Work equally well in cold or hot water. Long shelf life (unless exposed to light regularly). Iodines are non-irritating and don’t evolve vapors at standard temperature/pressure (iodine solutions just get more concentrated with evaporation). Iodine solutions maintain their disinfectant properties almost indefinitely until exposed to UV light or organic contaminants.

What’s bad about iodines:
Expensive. Stains some things quite badly. Tends to cloud plastics. Slightly corrosive in higher concentration. Inactivated by prolonged contact with organic matter.


Commercial sources of quaternary ammonium disinfectants:
Alpet D2
Roccal-D

What’s good about quaternary ammoniums:
Inexpensive. Very effective against all bacteria and most viruses. Odorless. Very low toxicity to higher life forms yet destroys %99.99 of microbial life (Alpet D2 is FDA approved for disinfecting food contact surfaces).

What’s bad about quaternary ammoniums:
Ineffective against spores. Decreased effectiveness in hard water. Highly ineffective in the presence of organic matter. Leaves a powdery residue. Ingestion of large amounts can cause respiratory paralysis/failure.


Detergents:
Chemicals designed to clean surfaces or objects (by reducing surface tension and placing dirt in suspension apart from the object to be cleaned) are called detergents. Detergents do not destroy microorganisms or spores. Detergents are most effective with physical stimulation (scrubbing). Sterilants and disinfectants do NOT make good detergents. Surfaces/tools that are not cleaned are far more difficult to sterilize and will contaminate quicker than clean instruments.

There are thousands of common detergents. Try to avoid solutions with perfumes and/or emollients as they tend to leave residues which can negatively affect your sterile procedures.

Good luck and happy culturing!

This is A+ info!!! Thanks for posting it!

[BuckarooBanzai]

Wow, thanks Freakachino! Props are always cool, but when they come from somebody whose work you respect...that's just the best! Picture a big 'ol goofy grin on my face...

As much as I have learned from you wonderful folks, I am very happy to contribute anything I can. How often do you find such an amazingly interesting hobby with such a loving support group to ask questions of?

This community ROCKS!

[Hippie3]

archive material

[Venice]

excellent...thanks for your hard work!