Which patients with diarrhea should be started on empiric antibiotic therapy? Which antibiotic?

Patient's with any of the following characteristics should be started on a fluroquinolone for three to five days.

• travelers' diarrhea
• signs and symptoms  of invasive bacterial diarrhea such as fever and bloody diarrhea (EXCEPT in cases of suspected or proven infection with enterohemorrhagic E. coli which often presents with bloody diarrhea, abdominal pain and tenderness but little or no fever.  In these cases antibiotics may precipitate HUS)
• elderly/immunocompromised 

Source

Wanke, C.  "Approach to the adult with acute diarrhea in developed countries"  Up to Date. 2 June 2010.