eTopic 27.1 Antibiotic Spectrum of Activity

Effective treatment of a bacterial infection requires the use of an antibiotic that possesses the proper spectrum of activity. It would be ill-advised, for instance, to treat a Gram-negative infection with vancomycin because vancomycin is effective in killing only Gram-positive bacteria. Generally, when physicians are unclear whether an infection is caused by a Gram-positive or a Gram-negative bacterial species, they will start treatment with a broad-spectrum antibiotic. The table below lists some commonly used antibiotics with their spectrum of activity against aerobic and anaerobic pathogens.


a ±, variable activity, depending on species/strain.