The news agency interviewed Juan Carlos Dalto, chief executive of Dannon, a unit of France's Groupe Danone.
Dalto said that approximately one quarter of its DanActive and Activia brand sales come from new customers.
The rest, he told Reuters, are sales that are taking away from other brands of Dannon.
The company has been the probiotic trailblazer for the US, bringing the friendly bacteria to the company via a massive marketing campaign it began two years ago.
Since Activia's launch in January 2006, it has surpassed $100m in retail grocery sales in the US.
Dannon cited the global sales of probiotics yogurts and dairy drinks market are valued at approximately $10bn and this figure it set to grow.
These sales were not easily won as probiotic suppliers faced resistance in North America, where the concept of 'friendly bacteria' did not take off as quickly as in Europe.
Activia is a lowfat probiotic yogurt containing Dannon's proprietary probiotic culture, which the company says has been clinically shown to help regulate the digestive system when eaten daily for two weeks.
Dalto said the company will extend its Activia line with the launch of Activia Light - a fat-free, reduced calorie version of the probiotic yogurt.
This year Dannon also launched DanActive, a cultured probiotic dairy drink geared towards strengthening the body's defenses when consumed daily.
DanActive contains the proprietary probiotic L. casei Immunitas culture.
Previously only available in test markets in the US, DanActive is sold to the sound of more than six million bottles a day around the world.
The drink was first introduced in Europe in 1994 and later Asia under the brand name Actimel.
According to Dalto, the company's sales have brought growth despite the need to offset increasing prices in the dairy world.
"I think we are very decently protecting and defending ourselves from the unprecedented cost increase," he told the news agency.