Antibiotics should be used only when an infection susceptible to the antibiotic is present or suspected. While this may sound obvious, many times doctors will prescribe and/or patients will demand antibiotics for conditions that are not caused by organisms that can be treated with these types of drugs. A common example is the patient who demands an antibiotic for a cold. The common cold is due to a variety of viruses that do not respond to any currently available antibiotics. Use of an antibiotic in this situation does not benefit the patient and exposes him or her to potential toxicity from the drug. More importantly this practice helps select bacteria resistant to antibiotics by killing off nonresistant bacteria. It is critical for doctors and patients alike to be aware that not all infections need antibiotic therapy.
If the patient appears to have an infection, the physician needs to determine its type and location, to begin to figure out the type of organisms involved. Appropriate cultures and radiographic studies are obtained as necessary. If the physician believes that treatment with antibiotics is indicated, an antibiotic covering the most likely organisms associated with the infection is chosen. For example, the types of bacteria commonly causing a urinary tract infection are quite different from those associated with a sore throat. The physician must also decide whether the patient can be treated with antibiotics administered orally or intravenously or whether the patient requires admission to the hospital or can be treated on an outpatient basis.
When antibiotics are chosen based on the most likely type of bacteria, this is called "empiric therapy." Generally, empiric therapy is designed to cover a number of different organisms. Once the laboratory data return with more specific information about the infecting bacteria, the antibiotics can be adjusted to cover the organisms involved in the infection. Treatment of a specific organism is termed "directed therapy." At this point the physician must decide whether to continue the same antibiotic that was started empirically at the onset of therapy or whether a different antibiotic should be used. Physicians may wish to change to antibiotics that are more specific for the particular organism, especially if they are better tolerated or safer for the patient.
Once antibiotic treatment is started, it is very important that patients continue to take their antibiotic therapy as prescribed. One of the major factors in selecting out resistant organisms is patients discontinuing their antibiotic therapy too soon or taking the medication intermittently. This has been a particular problem with tuberculosis and has resulted in emergence of multidrug resistant bacteria.
Antibiotics can also be used to prevent infection. This is called prophylaxis and is commonly used before surgery to prevent postoperative wound infections. Although use of antibiotics in this manner has been shown to decrease the incidence of postoperative infection, prophylaxis does not eliminate such infections. In addition, inappropriate antibiotic prophylaxis has contributed to the development of bacteria resistant to antibiotics. The timing of prophylactic antibiotics is critical to their efficacy, and short courses of antibiotics have been found to be as effective as longer courses.