BARCELONA - American teenager Missy Franklin became the first woman to win six golds at a single world championships when she helped the United States to victory in the 4x100 meters medley relay on Sunday.The 18-year-old swam the opening, backstroke leg in the hilltop pool in Barcelona and the US triumph followed her titles this week in 100 and 200 backstroke, 200 freestyle and the 4x100 and 4x200 freestyle relays.She was fourth in Friday's 100 freestyle."It hurt really, really bad but now we're all done and we're all super excited," a still-dripping Franklin, who is due to sign on at University of California, Berkeley later this year, told reporters."I think I'm going to take my time off until I get to Berkeley so I think that gives me about two and a half weeks. We're all pretty excited about it."Franklin's sixth gold is one more than the previous record of five she jointly held with compatriot Tracy Caulkins and Australia's Libby Trickett.