Question

What is a negative effect of widespread use of antimicrobial soaps? What are the most effective ways of eliminating harmful contaminating agents, especially when dealing with contaminants such as HIV, anthrax, and prions?

Answer 1

1. Soap cause loosening and lifting of dirt, oil and microbes from surfaces. These can then be easily rinsed away with water. Antimicrobial soaps kill the microbes before they are washed off.

Continuous use of antimicrobial soap, however, increases the possibility of resistance to antimicrobials. Bacteria can develop resistance when exposed to the substance for a long time by developing mutations. When the soap is used frequently, bacteria present on skin surface may develop resistance. Hence, they are able to colonize the skin and cause infections. These infections are difficult to treat due to antimicrobial agents used.

2. Prions are infectious agents causing slow, progressive and fatal diseases of the central nervous system. Prions can cause degenerative brain diseases, such as scrapie, mad cow disease, Creutzfeldt Jacob disease (CJD) and Gertsmann-Straeussler-Scheinker (GSS) disease. Prions are resistant to more conventional methods of inactivation. Prions can be removed by sterilization of articles or specimens 134-138°C for 18 minutes at in a pre-vacuum pressure steam sterilizer or 1 hour at 132°C in a downward displacement pressure steam sterilizer. When sodium hypochlorite dissolves in water, it forms hypochlorous acid (HOCl) and the hypochlorite ion (OCl-). Hypochlorous acid forms hydrochloric acid (HCl) and oxygen (O). The oxygen atom is a very strong oxidator and can kill microorganism. Decontamination of prions can be done with 20,000 ppm of sodium hypochlorite for 1 hour. Contaminated material should be kept wet at time of use or disinfection as drying will promote ineffectivity of the chemical.

Anthrax is caused by Bacillus anthracis. This bacteria forms spores that are highly resistant to chemical and heat disinfection. Soil can be disinfected with 12.5% formalin solution (5% formaldehyde) at 50 litres/square meter. Equipments can be decontaminated using 10-30% formalin for 30 min. Formalin at 10-30% can kill anthrax spores.

Human immunodeficiency virus (HIV) causes AIDS in humans. It is transmitted via biological fluids such as blood and semen. Gloves should be used when handling HIV infected samples to prevent exposure to biological fluids. 0.5% sodium hypochlorite is used in hospitals to disinfect surfaces. Boiling in water at 100⁰C (hot water) for 20 min will kill the virus. Surgical instruments can be decontaminated by autoclaving at 121⁰C for 20 min or by steam sterilization.