The term broad-spectrum antibiotic refers to an antibiotic with activity against a wide range of disease-causing bacteria. This is in contrast to a narrow-spectrum antibiotic which is effective against only specific families of bacteria. A good example of a commonly used broad-spectrum antibiotic is levofloxacin.

Uses

Broad-spectrum antibiotics are properly used in the following medical situations:

• Empirically prior to identifying the causative bacteria when there is a wide differential and potentially serious illness would result in delay of treatment. This occurs, for example, in meningitis, where the patient can become so ill that he/she could die within hours if broad-spectrum antibiotics are not initiated.

• For drug resistant bacteria that do not respond to other, more narrow-spectrum antibiotics.

• In super-infections where there are multiple types of bacteria causing illness, thus warranting either a broad-spectrum antibiotic or combination antibiotic therapy.

There has been a common usage of broad-spectrum agents in treatment of community acquired infections without attempting to culture or otherwise identify the causative bacteria. Over the years, this practice has contributed to the emergence of more drug resistant strains of bacteria, necessatating the development of newer broad-spectrum antibiotics.

Ideally, the spectrum should be "narrowed down" by identifying the causative agent of an infection, and then replacing the broad-spectrum antibiotic with an appropriate narrower-spectrum antibiotic. This is believed to limit the development of antibiotic resistance, although evidence for this practice is unclear.