A 32-year-old woman comes to the physician for a health maintenance examination. She has been well and has no specific complaints. She eats a well-balanced diet and exercises on a stationary bicycle 3 days a week. She works as a nursing assistant at a local hospital. Review of her records shows that she is due for her annual influenza vaccination. Prior to administration of the vaccine, her skin is disinfected with 70% isopropanol. Which of the following mechanisms is most likely responsible for the antiseptic properties of isopropanol?
Commonly used clinical disinfectants | ||
Agent | Mechanism | Sporicidal |
Alcohols (isopropanol, ethanol) |
| No |
Chlorhexidine |
| No |
Hydrogen peroxide |
| Yes |
Iodine |
| Yes |
Alcohols, including ethanol and isopropanol, are widely used as disinfecting agents in the health care setting. They are commonly used to clean the skin before immunization or venipuncture and to disinfect external surfaces of equipment. They function by disorganizing the lipid structure in membranes, causing them to be leaky, and by denaturing cellular proteins. Alcohols require the presence of water for maximal activity and are most effective at 60%-90% concentration. They are rapidly bactericidal and also tuberculocidal, fungicidal, and virucidal, but do not destroy bacterial spores.
(Choice A) Chlorhexidine works by destabilizing cell membranes and coagulating intracellular constituents. In combination with 70% alcohol, it is the antiseptic of choice for many surgical and percutaneous procedures. Its use is contraindicated in neurologic, otologic, and ophthalmologic procedures due to neurotoxicity.
(Choice B) Formaldehyde and glutaraldehyde function by alkylating and cross-linking DNA and proteins. They are most commonly used for sterilization of hospital instruments that cannot withstand autoclave temperatures.
(Choice D) Iodine causes halogenation of proteins and DNA. Solutions containing iodine are frequently used for antisepsis in surgical and percutaneous procedures. However, they are less effective than chlorhexidine-alcohol and cause more skin irritation and toxicity.
(Choice E) Hydrogen peroxide functions as an oxidant by producing hydroxyl free radicals that attack cellular components. It is excellent at disinfecting inanimate objects but is less effective when used on organic materials. Hydrogen peroxide is often used for skin cleansing and wound debridement due to its effervescent quality.
Educational objective:
Alcohols function by disorganizing the lipid structure in membranes, causing them to be leaky, and by denaturing cellular proteins. They are bactericidal, tuberculocidal, fungicidal, and virucidal, but do not destroy bacterial spores.