Introduction:
In many different industries the elimination of microorganisms from inanimate objects or surfaces is critical to safety. (Please review terminology covered in Lab 6). Disinfectants and antiseptics often work slowly on certain viruses and endospores may be difficult to destroy, sterilization may not be practical. Results are generally better when initial microbes numbers are small and the surfaces being disinfected are relatively free of interfering substances. Disinfectants and antiseptics may damages the lipids / proteins of the cytoplasmic membrane of the organisms resulting in the cell leaking, or they may denature enzymes and proteins; affecting metabolism.
Common chemical agents:
1. Phenol and phenol derivatives. Phenols were the first disinfectants commonly used, but due to toxicity and odor, phenol derivatives are now generally used. These alter membrane permeability and denature proteins. These kill most bacteria & fungi, some viruses, but are generally ineffective against endospores.
Examples: Othophenylphenol – Lysol, O-syl, Stpahene, Amphyl
Hexachlorophene – PhisoHex
Triclosan – antimicrobial soaps
Hexylresorcinol – thoat lozenges
Chlorhexidine – handwashing / surgical scrub
2. Soaps & Detergents: Soaps are mildly microbicidal and aid in the mechanical removal of microbes by emulsifying the oily film on skin and reducing the surface tension of water. Anionic detergents mechanically remove microbes and other materials but are not very microbicidal. Cationic detergents alter membrane permeability and denature proteins. They are effective against many vegetative bacteria, some fungi and viruses, but endospores are generally resistant. They are inactivated by soaps and some other organic materials.
Examples of cationic detergents: benzalkonium chloride, zephiran, diaprene, roccal, ceepryn, phemerol
3. Alcohols: (ethyl, isopropyl): denature membranes, often combined with other disinfectants, usually kill vegetative bacteria, enveloped bacteria, & fungi, do not generally kill endospores or non-enveloped viruses
4. Acids / Alkalies: alter membrane permeability, denature proteins / other molecules, organic acid salts such as calcium propionate, potassium sorbate, and methyl paraben are used as food preservatives, undecylenic acid (Desenex) for skin infections, lye (sodium hydroxide) in soap
5. Heavy metals: (Hg, Ag, Cu): denature proteins, mercury compounds are bacteriostatic & do not skill enodspores, silver nitrate is used to prevent neonatal gonococcal ophthalmia, copper sulfate is used as a plant fungicide, and selenium sulfide is used as a fungicide
6. Chlorine: denatures enzymes, sodium hypochlorite is in household bleach, sodium hypochlorite & chloramines are used to sanitize glass & food equipement.
7. Iodine & iodophores: denature proteins, effective against vegetative bacteria, Mycobacterium tuberculosis, fungi, some viruses & endospores, (Wescodyne, loprep, loclide, betadine, isodine)
8. Aldehydes: denature proteins, formaldehyde & glutaraldehyde, formalin kills most microbes and is used in embalming, vaccines, and preparation of biological specimens, glutaraldehydes kill vegetative bacteria & endospores in 4 hours and are used in cold sterilization (Cidex, Sonacide, Sporocidin)
9. Ethylene oxide: denatures proteins, used in chemical sterilization after 4-12 hours, used for head sensitive items, very toxic and carcinogenic
Procedures:
Procedure:
Is that surface as clean as you think it is?
1. Swab a surface you intent to clean using a sterile swab, and then inoculate half of the plate.
2. Use the household cleaner you wish to test to clean the surface as you would normally use the product.
3. Swab the cleaned surface using a sterile swab & then inoculate the other half of the plate.
Are you sure your hands are clean?
1. Divide a plate of trypticase soy agar in half. Inoculate half the plate using your finger or a swab from your uncleaned hand.
2. Use your favorite hand sanitizer to clean your hands as you normally would.
3. Repeat the procedure used in step one to incoluate the other half of the plate with your “sanitized” hand.
To kiss or not to kiss?
1. Divide a plate of trypticase soy agar in half. Innoculate the entire plate using a sterile swab rubbed on one of your teeth.
2. On 1 half of the plate, use a sterile swab to apply your favorite tooth paste or mouthwash to 1 half of the plate. The other side will be a control.
3. You may wish to run a separate control swabbing a sample of your tooth paste or mouthwash since these items are frequently contaminated by your toothbrush or taking mouthwash directly from the mouth of the bottle.
Expected Results:
Sorry, I enjoy seeing the look on your face way too much to give this one away!
