Abstract: Methods, for the treatment of humans and lower animal subjects having a gastrointestinal disorder, comprising administering bismuth and administering an antimicrobial. From about 50 to about 5000 milligrams of bismuth are administered, per day, for from 3 to 56 days. A safe and effective amount of antimicrobial is administered for from 1 to 21 days. Preferred processes also include a step for performing a diagnostic test on the subject for detection of a campylobacter-like organism infection of the subject. The invention also provides compositions containing a safe and effective amount of bismuth and a safe and effective amount of antimicrobial.