What Is the Antibiotic Spectrum?

The antibiotic spectrum is the range of organisms against which an antibiotic is known to be effective. In the case of broad spectrum medications, the drug works on a wide number of organisms. Drugs on a narrow spectrum work only against specific families. Individual medications can work in a number of ways, to actively kill bacteria or inhibit their growth and bring an infection to a stop. Options for therapy can depend on the nature of an infection.

Charts with the antibiotic spectrum typically organize related organisms together, because they tend to be susceptible to the same kinds of medications. If a medication has a broad spectrum, it may be able to attack organisms in a large number of families across the antibiotic spectrum. Others may target specific families or closely related groups, and extend across a much shorter distance.

Broad spectrum antibiotics can be useful when a patient is infected with multiple organisms, or a doctor is not sure about the cause of an infection. In addition, such drugs tend to be more effective against resistant microbes. The drawback to using a broad spectrum antibiotic is that it can also cultivate drug resistance if it is not used properly. These aggressive medications can come with an increased risk of side effects, as well.

Doctors may choose to narrow down on a small segment of the antibiotic spectrum with a drug that specifically targets particular organisms. If an organism is naive, meaning it hasn’t been exposed to antibiotics before, these drugs may be highly effective. Before recommending a narrow-spectrum drug, care providers might consider a culture to confirm the identity of what is causing the infection. This can assure that patients get the right medication on the first try, instead of receiving an ineffective drug that allows the infection to continue raging.

Researchers in the field of antibiotics test new drugs against the antibiotic spectrum to find out their range of efficacy. This information is important for clinical trials as well as formal drug documentation. The results of tests and studies will enter the record associated with the drug to allow care providers to determine if it is appropriate for a given patient. If a drug stops working against a certain class of bacteria, this can be an indicator of antibiotic resistance. Additional research may be necessary to confirm and develop alternative medication recommendations to treat patients with those infections.