The 22-year-old had already set Australian records in both the 200 and 400 metres individual medleys in the last two days, and swam 27.07 seconds in the 50 metre backstroke to set a new all-comers record, the fastest time ever recorded in Australia.
McKeown, the reigning Olympic 100 and 200m backstroke champion, broke the world record in the same event in Budapest last year with a time of 26.86 seconds.
Mollie OCallaghan set a personal best of 27.16, matching McKeowns previous all-comers record, to take the silver medal, having won gold in the 100 metres freestyle and backstroke at the event.
Titmus, world record holder and Olympic champion, impressed when winning the 400 metres freestyle in a time of 3:59.13, the best time in the world this season, and the Australians first sub-four minute performance of the season.
