Antibiotics are lifesaving medicines and generally safe, yet unwanted side effects are common. While destroying illness-causing 'bad' bacteria, antibiotics can upset the protective 'good' bacteria in the body. This research will test if taking a probiotic with prescribed antibiotics will decrease the chance of having bothersome antibiotic-associated side effects.

Objectives Several studies have demonstrated that probiotics can be helpful in preventing antibiotic-associated diarrhoea in hospitalized patients. However, the extent to which probiotics may benefit healthy adults taking a course of antibiotics has not been investigated in primary care. Furthermore, patient willingness to take a probiotic supplement concomitantly with antibiotics has not been explored. We aimed to conduct an exploratory study using probiotics in adults requiring an acute course of antibiotic therapy.

Methods Patients prescribed antibiotics for treatment of acute infections in an outpatient family practice setting were randomized to receive either a probiotic or placebo concurrently. Patients completed adherence diaries and daily symptom checklists to assess gastrointestinal and vaginal (women) symptoms and collect information about adherence.

Inclusion Criteria:

• adults 18 - 79 years of age with infection requiring an oral antibiotic.
• Must be able to be contacted via telephone.

Exclusion criteria:

• pregnancy,
• breast-feeding,
• those receiving tube feeding,
• those with diarrhea as a current symptom of present illness, and pre-existing illnesses that contribute to diarrhea such as inflammatory bowel disease,
• irritable bowel syndrome, colitis or celiac disease.
• Those undergoing active cancer treatments with chemotherapeutic or radiation therapy,
• immunocompromised persons,
• history of cardiac valvular disease,
• those taking a laxative or stool softener on a daily basis, as well as
• persons treated with an antibiotic in the previous 60 days,
• new antibiotic prescription that exceeds a 10 day course, or regular use of a probiotic within the previous three weeks (including daily ingestion of yogurt).