70% Isopropyl Alcohol

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70% Isopropyl Alcohol


Isopropyl alcohol when mixed with water is a rapid antimicrobial (Davies et al., 1978). Concentrations between 60%-90% are most effective (Morten, 1950, Ali, Dolan, Fendler, & Larson, 2001). It is effective against bacteria (gram negative and gram positive), fungi and viruses. It is not effective bacterial spores and hydrophilic viruses (Klein & DeForest, 1963 as cited by Rutala et al., 2008). The mechanism alcohol uses to kill microbes is denaturing proteins in its fluid state. Evaporation limits its ability to kill microbes; it is not the mechanism used to kill them. Different microorganisms require different contact time although it seems from Johnston et al. (1987) that many microbes are killed in the first minute.

Information from- Block, S.S. (1991) Disinfection, Sterilization and Preservation (4 ed.) Gainesville, FL: University of Florida. (This book is in the HEC library collection and should be moving over to the School of Veterinary Technology library soon.) And Rutala, W.A., Weber, D.J. and the Healthcare Infection Control Advisory Committee (HICAC) (2008). Guidelines for Disinfection and Sterilization in Healthcare Facilities, CDC. (This article I sent to all veterinary technology faculty last semester.)

Topically no toxic effects (Grant, 1923)

Toxic effects by inhalation; “vapors may be absorbed through the lungs and produce narcosis” (Senz & Goldfarb, 1958, p. 196)

Staphylococcus aureus killed in 1 minute; Escherichia coli killed in 5 minutes ; spored cultures of Bacillus subtilis and Clostridium novyi not killed in 60 minutes; alcohol contaminated by saprophytic spore-forming organism: does not kill bacterial spores (Powell, 1945)

Sporicidal activity increased by adding 5% propylene oxide and maintaining temperature of 30 degrees C (Hart & Ng, 1975)

Staphylococcus aureus killed in less than 10 seconds with a 50% Isopropyl Alcohol solution and was not killed in 2 hours with a 90% solution: emphasizing the importance of water in killing microorganisms (Tainter et al., 1944)

Inactivation of Hepatitis B (Bond et al., 1983)

Inactivation of HIV in 35% solution in 2-10 minutes (Martin et al., 1985)

Loss of HIV ability to infect with 70% solution in 1 minute (Resnick et al., 1986)

Soaking in 70% solution 15 minutes destroyed vegetative bacteria on endotracheal tube cuffs (Zieglar & Jacoby, 1956)

70% isopropyl alcohol preparations for surgical scrub are efficacious; superior activity reducing bacterial populations under nails (Gross et al., 1979, McGinley et al., 1988, Larson et al., 1990)

Greater than 99% immediate reduction in bacterial counts from human abdominal skin (Davies et al., 1978)

Bacterial recolonization on skin: in 1 minutes still reduced by 99%; to keep recolonization down add an iodophor infused drape- significant reduction of recolonization for 60 minutes (Johnston et al., 1987)

”Spaulding who demonstrated using the mucin-loop test that 70% isopropyl alcohol destroyed 104 M. tuberculosis in 5 minutes…” (Rutala et al., 2008)

“isopropyl alcohol and ethyl alcohol have been excluded as high-level disinfectants because of their inability to inactivate bacterial spores and because of the inability of isopropyl alcohol to inactivate hydrophilic viruses (i.e., poliovirus, coxsackie virus).” (Rutala et al., 2008)

“These alcohols are rapidly bactericidal rather than bacteriostatic against vegetative forms of bacteria; they also are tuberculocidal, fungicidal, and virucidal but do not destroy bacterial spores. Their cidal activity drops sharply when diluted below 50% concentration, and the optimum bactericidal concentration is 60%–90% solutions in water (volume/volume)” (Rutala et al., 2008)

“The most feasible explanation for the antimicrobial action of alcohol is denaturation of proteins. This mechanism is supported by the observation that absolute ethyl alcohol, a dehydrating agent, is less bactericidal than mixtures of alcohol and water because proteins are denatured more quickly in the presence of water 484, 485. Protein denaturation also is consistent with observations that alcohol destroys the dehydrogenases of Escherichia coli 486, and that ethyl alcohol increases the lag phase of Enterobacter aerogenes 487 and that the lag phase effect could be reversed by adding certain amino acids. The bacteriostatic action was believed caused by inhibition of the production of metabolites essential for rapid cell division.” (Rutala et al., 2008)

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