Robert Keith Larson alleges that the board of directors and executives touted the company as highly successful with solid earnings and a successful business model. But a story in The Wall Street Journal revealed "the underlying unsustainability of the company's business model and the company was in fact perpetrating a 'pyramid scheme' in an attempt to sell its products," according to the lawsuit filed Tuesday. That story and a subsequent one at Forbes.com were based on the work of Barry Minkow, an investigator who spent time in prison for securities and tax fraud but now runs a business known as the Fraud Discovery Institute.

Three other lawsuits against Usana are pending in U.S. District Court for Utah based on Minkow's investigation. Usana vigorously denies the allegations and has sued Minkow, alleging he sought to profit by driving down the price of the company's stock.

After the March 15 Journal story, shares of the company fell 15 percent and by Aug. 8 had dipped to $29.48. Shares traded at $41.60 at the market close Wednesday, down from its 52-week high of $61.80.

Also Wednesday, Usana Health Sciences said it has appointed Pricewaterhouse-Coopers as the company's new independent accounting firm.

PricewaterhouseCoopers is expected to immediately begin reviewing the company's financial results for the second quarter that ended June 30. The Nasdaq stock exchange last month told Usana it could be delisted because its latest quarterly report was not reviewed by an independent auditor.

The company's auditor, Grant Thornton, resigned July 10, apparently over questions related to Minkow's report and before an accounting firm audited second quarter results.