Simple cases of Salmonella food poisoning are usually treated by encouraging good fluid intake, to avoid dehydration. Although the illness is caused by a bacteria, studies have shown that using antibiotics doesn't really shorten the course of the illness. Instead, antibiotics have the adverse effect of lengthening the amount of time the bacteria appear in the feces, thus potentially increasing others' risk of exposure to Salmonella.
Antibiotics are used when Salmonella causes more severe types of infection. In these cases, ampicillin, chloramphenicol, or quinolones can be taken by mouth, or given through a needle inserted in a vein (intravenously).