Antimicrobial Soaps

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Antimicrobial Soaps

Introduction

Antimicrobial soaps refer to solutions that are designed to lessen the number of living (viable) microorganisms on the surface of the skin. As they are usually rubbed on the skin during handwashing, the most common form of the antimicrobial product is a soap.

The main target of antimicrobial soaps are the bacteria that commonly live on (colonize) the surface of the skin. These include bacteria in the genera of Staphylococcus and Streptococcus. Normally, these bacteria are innocuous; they do not cause harm to the host. But, if they gain access to niches inside the body due to a cut or other injury, they can cause serious and even life-threatening diseases. An example is the contamination of implanted heart valves by Staphylococcus aureus, which can cause endocarditis. By handwashing with an antimicrobial soap for an adequate length of time (at least one minute) to lessen the number of living S. aureus on the skin prior to heart valve surgery, a surgeon can diminish the risk of infecting the patient.

Antimicrobial soaps are also a common part of the home. The ubiquitous bar of soap in the shower and by the bathroom sink is an example of an antimicrobial soap.

History and Scientific Foundations

The use of antibacterial soap began in the mid-nine-teenth century. At that time, the Viennese physician Ignaz Semmelweiss (1818–1865) noted the markedly higher death rate among hospitalized patients who received care from medical students, versus patients cared for by midwives. Semmelweiss determined that it was a common practice for the students to come from dissection and teaching labs to the hospital ward without washing their hands. By instituting a handwashing policy, the previous high death rate was almost completely eliminated.

With time came the knowledge that bacteria and other disease causing microorganisms such as fungi could be transferred from person to person on the skin of the caregiver. The use of antimicrobial compounds in soaps gained credence in the several decades following World War II (1939–1945), with the expanded use of antibiotics to treat bacterial diseases. The initial overwhelming success of antibiotics made the incorporation of antimicrobials into other products a health priority.

The principle ingredient that has been most commonly used in antimicrobial soaps is triclosan. The compound contains a phenol ring structure to which are attached chlorine groups. The phenol ring is very difficult to break apart, which means that bacteria and fungi are less apt to be capable of degrading the triclosan molecule to a form that is inactive. As well, chlorine has a potent antibacterial and antifungal effect.

Triclosan has many sites of action in bacteria and fungi, which can vary depending on the applied concentration of the compound. For example, at the concentrations typically found in antibacterial soaps, triclosan binds to and inhibits the activity of a variety of proteins and other cell components both in the bacterial or fungal membranes and in the cytoplasm—the dense fluid that fills the interior of the microorganisms. The cytoplasmic targets are mainly enzymes—proteins that function to speed up chemical reactions, including those that are vital to cell survival. The multiple inactivations caused by triclosan are too much for the bacteria or fungi to overcome and they are rapidly killed.

Another antimicrobial compound used in soaps is triclocarban. This compound also has ring structures and chlorine groups, and its antimicrobial activity is similar to that of triclosan.

Applications and Research

Antibacterial soaps are a standard feature of hospitals and other health care facilities, where the need to control the spread of infections is essential. For example, the use of antibacterial soap or other type of skin wash is very important in controlling the spread of a type of bacteria designated methicillin resistant Staphylococcus aureus (MRSA) from ward to ward in hospitals. This is because MRSA is resistant to many antibiotics, and so can be difficult to treat once present in a hospital. A patient whose immune system is not functioning efficiently can become extremely ill or can die if infected with MRSA.

Other triclosan containing products have become more widely popular in everyday life. Examples of commercially available antimicrobial soaps include the facial wash marketed as Clearasil®, which is designed to lessen the development of acne, and Dial Complete® soap.

Impacts and Issues

While antimicrobial soaps have been very effective in controlling the spread of infectious diseases, their overuse or misuse may be promoting the development of bacteria that are resistant to triclosan. Studies with Escherichia coli have indicated that the genetic alterations that render the bacteria resistant to triclosan might also confer resistance to other antibacterial compounds including some antibiotics. Put another way, the use of antimicrobial soaps may drive the bacteria to become more resistant and so a greater threat to health.

WORDS TO KNOW

COLONIZATION: Colonization is the process of occupation and increase in number of microorganisms at a specific site.

RESISTANT ORGANISM: Resistant organisms are bacteria, viruses, parasites, or other disease-causing agents that have stopped responding to drugs that once killed them.

TRICLOSAN: A chemical that kills bacteria. Most antibacterial soaps use this chemical.

IN CONTEXT: EFFECTIVE RULES AND REGULATIONS

Disinfection is a key strategy of infection control. Disinfection refers to the reduction in the number of living microorganisms to a level that is considered to be safe for the particular environment. Typically, this entails the destruction of those microbes that are capable of causing disease.

Disinfection is different from sterilization, which is the complete destruction of all microbial life on the surface or in the liquid. The steam-heat technique of autoclaving is an example of sterilization.

There are three levels of disinfection, with respect to power of the disinfection. High-level disinfection will kill all organisms, except for large concentrations of bacterial spores, using a chemical agent that has been approved as a so-called sterilant by the United States Food and Drug Administration. Intermediate level disinfection is that which kills mycobacteria, most viruses, and all types of bacteria. This type of disinfection uses a chemical agent that is approved as a tuberculocide by the United States Environmental Protection Agency (EPA). The last type of disinfection is called low-level disinfection. In this type, some viruses and bacteria are killed using a chemical compound designated by the EPA as a hospital disinfectant.

An important reason has been the expansion in the use of triclosan containing soaps in the home. Consumers have become more conscious of the possible health threat of microorganisms and the marketplace has responded by formulating products designed for everyday use. Unfortunately, if a microorganism is exposed to a sub-lethal concentration of triclosan, or not exposed to the compound long enough due to inadequate washing (the soap needs to be present on the skin for 30–45 seconds), the microbe may survive and become more resistant to the antimicrobial agent. If this resistance has been acquired because of a genetic alteration, the trait can be passed to future generations of microorganisms.

IN CONTEXT: PERSONAL RESPONSIBILITY AND PROTECTION

Improper handwashing can be dangerous. Particularly harsh soaps, or very frequent handwashing (for example, 20–30 times a day) can increase the acidity of the skin, which can counteract some of the protective fatty acid secretions. Also the physical act of washing will shed skin cells. If washing is excessive, the protective microflora will be removed, leaving the newly exposed skin susceptible to colonization by another, potentially harmful microorganism. Health care workers, who scrub their hands frequently, are prone to skin infections and damage.

IN CONTEXT: EFFECTIVE RULES AND REGULATIONS

In October 2005, a U.S. Food and Drug Administration panel advised that washing with popular antibacterial soaps and gels in the home was no more effective in preventing infections than washing with plain soap and water. The panel is currently considering recommendations for stricter rules in advertising and labeling of antibacterial products. The panel excluded alcohol-based antibacterial gels from the advisory, which were considered useful in preventing infections where adequate soap and water were not accessible.

The link between triclosan resistance and resistance to other agents is contentious. While some studies published since 2003 have not found evidence of a link, other studies have. For example, triclosan has been demonstrated to be capable of blocking the manufacture of fatty acids, molecules vital to the construction of membranes. The altered membrane can make some bacteria resistant to antibiotics that formerly killed them.

The expanded and less controlled use of antimicrobial soaps is also a concern in light of a study published in 2006 that demonstrated that low doses of triclosan in the environment from domestic wastes cause hormonal alterations in the North American bullfrog. This indicates that there may be detrimental changes associated with the discharge of low levels of antimicrobial soaps into the environment.