Legionella Testing / Biosafety Training


Dr Richard W Gilpin’s Blog

70% IPA or Ethanol? - Bleach Instead? Disinfectants for BSC Work

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 without washing is a potential fungal contamination issue. 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, biological indicators are frequently shipped in alcohol solutions. Article entitled;  “Changing the Paradigm of Cleaning and Disinfection in Cleanrooms” Read more>

Isopropyl alcohol and ethyl alcohol have been excluded as high-level disinfectants because of their inability to inactivate bacterial or fungal spores and because of the inability of isopropyl alcohol to inactivate hydrophilic viruses (i.e., poliovirus, coxsackie virus).  Read more>

70% alcohol evaporates rapidly (within 10-15 seconds) inside operating biosafety cabinets (BSCs) and can carry spores in the alcohol-free water into BSC work areas if alcohol is sprayed on gloves or equipment.

Alcohols attack acrylic, polypropylene, PVC, and polycarbonate plastics.

Vinyl and natural latex gloves are 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?
Take a look at Controlled Environments Magazine 17(8)16-19, September 2014.

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 that is corroded by to bleach. Two commonly used types of stainless steel coupons were exposed to household bleach 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.  Bleach diluted at 1:10 and 1:50 showed corrosion of the stainless steel.  Coupons exposed to NaDCC solutions at levels of 187 and 937 ppm active chlorine did not show corrosion, suggesting that NaDCC can serve as an effective alternative disinfectant to liquid bleach.

 Legionella topic of the day: Legionella pneumophila has cytochrome o, but lacks cytochrome a.
Cytochrome o is probably the terminal oxidase.
Kronick, P.L. and R.W. Gilpin. 1980. Cytochrome spectra of Legionella pneumophila.  Microbios. Lett. 14:59-63. Read more>