Science of Resistance: Antibacterial Agents

When Louis Pasteur demonstrated that bacteria are the agents that cause many infections, people were better able to understand how diseases begin and spread. Ironically, however, even though Pasteur's findings demystified infectious disease, they also led to fear of "germ" contamination. This fear was not allayed until the last half of the twentieth century when antibiotics were discovered and used clinically.

Antibiotics were considered miracle drugs when they were first introduced. Many people felt that diseases caused by bacteria were conquered and soon would no longer exist. Unfortunately, however, because antibiotics were adopted as "wonder drugs," they were often used in indiscriminate and improper ways. Resistant strains of bacteria began to emerge. Today, roughly fifty years after antibiotics were introduced, antibiotic resistance is a serious problem and antibiotics are losing their effectiveness. In health facilities, epidemics of antibiotic-resistant infections are serious threats to those whose health is already compromised. Diseases such as tuberculosis, once felt to be under control, are often resistant to many antibiotics and frequently do not respond to treatment. Public concern about infection has been heightened; people are once again afraid of "germs." One response to this fear is greater public use of a variety of antibacterial agents designed to remove disease-causing organisms from external surfaces before they can enter the body. Although first introduced into soaps, detergents and other cleaning and health care products, today antibacterials may also be impregnated into sponges, cutting boards, carpeting, upholstery, and even children's toys.

Using antibacterial agents to destroy many organisms before they enter the body may not always be the best way to stop the spread of infectious disease. This is because we need "good" bacteria to control and compete with "bad" bacteria. We frequently encounter and touch disease-causing or "bad" organisms (as, for example when we touch the nose, the mouth, an open wound, or fecal matter—all sources of infectious agents). However, these bacteria must compete for space with the variety of "good" bacteria that we also carry on and in our bodies and that we encounter in the environment. This means that not all contacts we have with bacteria, even "bad" bacteria, result in disease. If we destroy all the bacteria on a surface, we will destroy both kinds, removing the "good" bacteria along with the "bad". Chemical agents don't discriminate between "good" and "bad" bacteria, and can remove all bacteria. However, if bacteria do remain, these may be resistant to the effects of the chemical agents.

In certain settings, antibacterial agents are essential to fight against infection. However, if used too frequently and indiscriminately, certain antibacterial agents—those that leave trace chemical residues and that target particular processes in the life cycle of bacteria—may, like antibiotics, select for resistant strains. To insure that these agents continue to be effective when they are needed, products containing these antibacterials should only be used when they are essential to fight against infection. In other situations, when more information is not available, it is wiser to disinfect with agents that are unlikely to select for resistant strains of bacteria.

Generally, the best way to remove "bad" bacteria is through good hand-washing practice using a non-bactericidal soap and water. Proper hand-washing will remove 99.9% of bacteria, and normally, few other control measures are needed. When susceptible populations are likely to be exposed to "bad" bacteria, other more effective control measures may be required. Settings involving susceptible populations: young children, the elderly, or those whose health is compromised because of AIDS infection, use of immunosuppressive drugs, illnesses requiring hospitalization, or chemotherapy require additional disinfection measures. Antibacterial agents should be reserved for these settings.


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