Every national federation can select three athletes for the World Championships or Olympics, providing they meet the 'A' standard, with only one allowed if they only meet the 'B' standard.
Before his run in Italy, Pistorius was only the fourth fastest South African - behind LJ van Zyl, Ofentse Mogawane and Lebogang Moeng - over the distance this year.
A time of 46.65secs in gusty conditions in Padua on Sunday had left Pistorius with only one more chance to qualify for the World Championships and his emphatic victory in Lignano resulted in him leapfrogging Mogawane and Moeng.
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