Ampicillin is a Broad-spectrum antibiotic in the class of drugs called penicillins. Ampicillin fights bacteria in your body. Ampicillin is used to treat many different types of infections, such as tonsillitis, pneumonia, bronchitis, urinary tract infections, gonorrhea, and infections of the intestines such as salmonella (food poisoning). Ampicillin may also be used for purposes other than those listed in this medication guide. If you are allergic to penicillin do not order this medication.