Everyone uses IPA disinfection – Don’t they?
70% isopropanol (IPA) or 70% ethanol is often used as a surface disinfectant, particularly in virology and tissue culture laboratories.
70% alcohol in a squirt bottle kept around for months and refilling without washing is a potential fungal contamination issue because fungi can use alcohol as a carbon source and grow.
When 70% alcohol is squirted from a squirt bottle, room air (including fungal spores) is pulled into the bottle as it returns to its original shape.
Fungal spores have been cultured from sediment at the bottom of alcohol squirt bottles.
Also, alcohol concentration decreases with time in a squirt bottle.
Alcohol is not sporicidal. In fact, bacterial spores used as biological indicators are frequently shipped in alcohol solutions.
Isopropyl alcohol and ethyl alcohol have been excluded as high-level disinfectants because of their inability to inactivate bacterial or fungal spores and hydrophilic viruses [i.e., poliovirus, coxsackie virus]. CDC-Read more> .
70% alcohol evaporates rapidly (within 10-15 seconds) when sprayed inside operating biosafety cabinets (BSCs). gloves, or equipment.
The spraying may carry bacterial/fungal spores onto the BSC work surfaces, gloves, or equipment, thus allowing migration of spores into the work materials such as tissue cultures .
Alcohols also attack acrylic, polypropylene, PVC, and polycarbonate plastics and will eventually make them brittle and unusable.
Vinyl and natural latex gloves are also permeated by alcohol in less than 10 minutes, but not by other organic-based disinfectants.
[Mellstrom, Lindberg & Boman. “Permeation and Destructive Effects of Disinfectants on Protective Gloves.” Contact Dermatitis 26:163-1709, 1992.] Read more> .
Stainless steel is corroded by chlorine bleach – This includes BSC work surfaces.
Are Your Stainless Steel Surfaces Being Corroded by Repeated Bleach Use?
The first sign of corrosion is the appearance of cloudy areas on stainless steel surfaces.
Bleach is known to be corrosive to metals that are commonly found in pharmaceutical, bioprocessing and medical device work environments.
Biosafety cabinets are made with code 304 stainless steel – Code 304 Stainless Steel is corroded by to bleach.
Experiments using two commonly used types of stainless steel coupons were exposed to household bleach [sodium hypochlorite] and sodium dichloroisocyanurate [NaDCC] solutions over a period of eight weeks.
The rate and degree of corrosion exhibited by the stainless steel coupons were compared.
Household bleach diluted at 1:10 and also 1:50 corroded the stainless steel.
Coupons exposed to NaDCC solutions at levels of 187 and 937 ppm active chlorine did not show corrosion.
NaDCC can serve as an effective alternative disinfectant to liquid bleach.
Recommendation – Use an Iodophor.
During my laboratory research career I have used an iodophor [WescodyneTM – Steris] diluted 1:250 in water as a BSC workspace disinfectant. I also use the iodophor to reduce growth in waterbaths.
The iodophor will leave a brown sheen on the work surface that has antimicrobial activity. If you spill drops on the work surface, a clear circle will form and show you where you have contaminated the work surface.