The shares of Costco (COST) are declining after Deutsche Bank downgraded the stock today, citing increased competition and fading catalysts. The rating change in the wake of Amazon's (AMZN) deal for Whole Foods (WFM) echoes concerns expressed by Goldman Sachs in its own downgrade of Costco on Friday.

DEUTSCHE DOWNGRADE: Analyst Paul Trussell downgraded Costco shares to Hold from Buy, stating that competition is intensifying as Amazon and Wal-Mart (WMT) are both launching new in-store and online initiatives at an accelerated pace. Amazon's takeover of Whole Foods is "a game changer," as it threatens Costco's "competitive moat in groceries," the analyst stated. Additionally, Trussell believes that Costco's online system is weaker than that of its peers, noting that its online sales rose only 11% year-over-year in its second and third quarters. The analyst added that several of the retailer's previous catalysts, including its special dividend and its switch to co-branded Visa (V) cards from American Express (AXP), have played out, while there do not appear to be "a pipeline of new catalysts." Trussell trimmed his price target on Costco to $172 from $187.

GOLDMAN: Analyst Matthew Fassler downgraded Costco to Neutral from Buy and removed it from his firm's Conviction List, arguing that Amazon's "ongoing interest in consumables," along with Costco's "fading...catalysts" will put a ceiling on Costco's stock. Costco's competitive advantage was based on its natural and organic food offerings, along with "consumables not easily available on Amazon," according to Fassler. In the wake of the Whole Foods deal, Amazon will probably be able to provide such items more efficiently and at lower prices than retailers that currently sell them, the analyst stated. Additionally, Fassler and Trussell agree on the status of Costco's positive catalysts, saying that they are "passed or are peaking." He cut his price target on the stock to $176 from $197.

PRICE ACTION: In morning trading, Costco fell 2% to $163.70. Over the last two sessions, Costco shares have declined over 9%.