Think twice before putting that lemon wedge into your cocktail, it’s likely covered in germs. Researchers from Clemson University looked at how bacteria and viruses travel on lemons and ice. They found when hands that were contaminated with E. coli handled wet lemons, the bacteria transferred 100% of the time. If the lemons were dry the bacteria transferred 80% of the time. The results were also dismal for ice – up to 67% of bacteria from hands transferred to ice, and 83% of bacteria from scoops transferred to ice. Also, previous research has shown you can’t count on alcohol to act as an antiseptic to gross lemons or ice, as most germs survived on contaminated ice until it melted. (KU.edu)
I've never understood why people would want to add fruit to their drinks, it just takes up room that could otherwise be filled with more alcohol...