What antibiotics should be empirically used to treat a foot cellulitis which began after walking in a body of water (stream, ocean, etc)?

First generation cephalosporin, levaquin and - depending on epidemiologic risk - flagyl if sewage-contaminated water or soil-contaminated wound and doxycycline if sea water exposure.

For cephalosporin allergic patients, substitute clindamycin. Given clindamycin's anaerobic coverage, no need for flagyl in these patients.

The above antibiotics cover the most common microorganisms that can produce soft tissue infections following water exposure including Aeromonas species, Edwardsiella tarda, Erysipelothrix rhusiopathiae, Vibrio vulnificus, and Mycobacterium marinum.


Source

Baddour, L. "Soft tissue infections following water exposure" Up to Date. 2011 Jan.