Steeplechase sensation, Jairus Birech and national champion Ronald Kwemoi, who is not a household name, maintained their purple patch in the men steeplechase and 1500m events.
Sum’s winning streak is even more impressive as her last loss was more than a year ago.
The world champion achieved another 800m victory in Lausanne, setting a season’s best of 1:58.48 in the process.
Pacemaker Agatha Jeruto led through the first lap in 54.96 but Sum passed the bell in 56.9 and maintained her lead to the finish.
Russia’s Olympic bronze medallist Ekaterina Poistogova came through strong on the final lap but had to settle for second in 1:58.79. Ethiopian teenager Tigist Assefa was third in a personal best of 1:59.24.
After the first lap of the women’s 3000m, it was clear that no one wanted to follow the pacemakers, who were aiming to set up the race for a finishing time in the region of 8:20.
Instead, the key contenders were happy to sit back and concentrate on winning.
World indoor champion Genzebe Dibaba kicked hard with 300 metres remaining and opened up a small gap, but she couldn’t quite shake off the rest of the field.
Cherono, the Worlds 5000m silver medallist moved on to her shoulder coming off the final bend and passed Dibaba with 50 metres to go, winning in 8:50.24.
Birech is fast making a habit of winning and in Lausanne he turned the men’s 3000m steeplechase into a one-man show.
After being led through 1000m in 2:39.80 and then passing 2000m in 5:21.62, it appeared as though Birech still had a chance to break the meeting record of 8:01.62.
However, with no one to challenge him, Birech had to be content with the win in 8:03.34.
More than eight seconds behind in 8:11.93, world silver medallist Conseslus Kipruto enjoyed a competitive return to action after being knocked out at semi finals of the Commonwealth Trials in Nairobi.
Kwemoi, 18, has never lost a 1500m race and he maintained that record in Lausanne when stunning a quality field that included 2011 world silver medallist Silas Kiplagat, Ethiopian record-holder Aman Wote, USA’s world silver medallist Matt Centrowitz and Morocco’s former world indoor champion Abdalaati Iguider.
Led by the pacemakers through 800m in 1:51.06 and 1200m in 2:50.06, Kwemoi kicked hard on the final lap to edge ahead of Kiplagat.
Unstoppable, the teenager continued to charge towards the line and stopped the clock at 3:31.48, the fastest time in the world by a junior for 10 years.
Kiplagat finished a few strides behind in 3:31.81 with James Magut, completing the sweep in 3:31.91.
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