Not too long ago, sexually transmitted infections in San Francisco were at an all time high. Then suddenly, they dropped, especially among gay men. Health officials believe the success is due to the roll-out of preventative antibiotics: a kind of morning-after pill for S-T-I's. But as KQED's health correspondent April Dembosky reports, scientists are worried that using antibiotics this way could lead to antibiotic reisistance, making it harder to treat infections down the road.