Croatia's Mirjana Lucic-Baroni, who made the third round of the 1997 US Open also at 15, was the previous youngest player to advance to that stage of a grand slam.
Top seed Sania Mirza quelled a late challenge from American wildcard Laura Granville to enter the quarter-finals of the US $75,000 ITF Vancuover Open on Thursday.
Jamaica's sprinting dominance continued in sizzling style on Monday when Olympic champion Shelly-Ann Fraser clocked 10.73 seconds to win the women's world 100 metres, 24 hours after Usain Bolt's 9.58 in the men's event. Kenenisa Bekele was again awesome as he won the 10,000 metres gold for the fourth time in a row but Yelena Isinbayeva's bid for a hat-trick of pole vault titles imploded when she failed to clear a height, allowing Poland's Anna Rogowska to take a shock gold.
Yelena Isinbayeva beat Russian team mate and bitter rival Svetlana Feofanova with a world record to claim the Olympic women's pole vault gold.
Images from the Australian Open matches played at Melbourne Park on Wednesday.