Costco would review the trial early next month.
If the trial was successful, the chain would do a nationwide launch of the product throughout its more than 400 stores, Blis chief executive Barry Richardson said in an interview.
"We will be doing everything possible to ensure they are happy with it. This is exciting news. It is good to see the evolution of these products. It is a good position for Blis to be in."
Blis develops and manufacturers products and ingredients for the oral healthcare market in New Zealand, Asia, Europe and the US.
The product being trialled by Costco, regarded as the fifth largest US retailer, was being sold under the brand name BioGuard.
It was developed for the US market by the publicly listed dietary supplement manufacturer Imagenetix Inc, to provide around-the-clock natural protection of the ear, nose and throat.
Dr Richardson said Imagenetix selected Blis K12 for its BioGuard because it met the high standards for both scientific support and credibility as well as being a "truly novel ingredient".
Blis provided Imagenetix with bags of stabilised bacteria which was used in the manufacture of BioGuard.
BioGuard was being sold in the dietary supplement section of Costco and was granted the status of FSA (flexible spending account).
FSA was set up by the US Government to enable US employers to provide a tax deductable and discretionary spending account for their employees to then purchase specific healthcare products and services of their own choosing.
"This is further evidence that the market strategy of focusing on the US dietary supplement market is working well for us.
"We chose to leverage our experience and knowledge from the New Zealand retail market over the past five years to assist our client companies in the US to succeed in bringing new retail products to the market."
Blis had become the recognised expert in the oral healthcare segment of the dietary supplements market, he said.
Asked to rate the Costco trial among the achievements of Blis, Dr Richardson said it was one of the big deals but there were several pending.
"The first big one was Nestle. This is the second one, and it is quite significant. With more than 400 stores in the US, they will have throughput we need to meet."
In addition to the Costco trial, US dietary supplement manufacturer Nature's Plus had successfully launched its first Blis M18 product called "Tooth Fairy", he said.
Blis M18 was an advanced oral-care probiotic which was specifically developed for the prevention of tooth decay.
Tooth Fairy was aimed at the children's oral care segment of the market and was launched in the US to coincide with the start of the new school year in early September.
Blis, and its global distribution partner Frutarom, continued to push business development activities in Asia and had just launched the first retail product in Japan to contain Blis K12.
The product, called EPOCA, was sold through the Japanese Health products distributor ISK Corporation.
Two new notices of intention to grant a patent had been received by the company from the European Patent Office, Dr Richardson said.
One notice related to Blis M18 and the associated prevention of tooth decay.
The other related to a probiotic that was still at an early state of development, but had shown to have promising antibacterial effects on skin.
Blis would announce its half-year earnings, for the six months ended September 30, late next month.
