What are broad-spectrum antibiotics?

Sometimes when you're sick, your doctor takes one look at you and knows exactly what's wrong and what medicine to prescribe. But other times, you may have symptoms that could be caused by several different bacterial infections, and it may be tough to tell the difference between them.

Fortunately, there are options in those situations. Instead of prescribing an antibiotic that works only against a select group of bacteria, your doctor can treat you with a course of a broad-spectrum antibiotic, which is effective against a wide range of infectious agents [source: Tufts]. Instead of narrow-spectrum medications such as penicillin or rifamycin, for example, your physician can turn to a broad-spectrum antibiotic such as chloramphenicol, one of the tetracyclines or the third-generation fluoroquinolones [sources: MSU, Chopra and Roberts].

Broad-spectrum antibiotics are particularly useful when a patient shows up at a hospital emergency room in dire distress, and doctors have to move quickly [source: Williams]. And they can be just as effective as narrow-spectrum antibiotics in treating disease. In a study published in 2005 in the medical journal Thorax, for example, researchers reported that patients with a type of pneumonia who took broad-spectrum antibiotics had the same results as those who were treated with a narrow-spectrum antibiotic that was specific to the disease, though they did experience more side effects [source: van der Eerden et al.].

In some ways, broad-spectrum antibiotics are the Swiss army knives of medical care. A study by the U.S. Centers for Disease Control and Prevention (CDC) in 2014 found that broad-spectrum antibiotics are the most commonly used antibiotics in hospitals throughout the U.S. But that comes with a significant downside. Because they kill microbes indiscriminately in a scorched-earth sort of attack, they wipe out beneficial ones, as well.

To make matters worse, broad-spectrum antibiotics also increase the possibility that some microbes will develop antibiotic resistance, health experts worry [source: HealthDay News]. For that reason, doctors generally try to quickly "de-escalate" broad-spectrum treatment and switch to a narrow-spectrum antibiotic as fast as they can [source: Williams]. In the future, they're hoping that better diagnostic tests will allow them to pinpoint a precise treatment more quickly [source: HealthDay News].