LOUISVILLE, Ky. -- Taco Bell's new take on the taco, featuring orange Doritos dust, has helped put the sizzle back in its U.S. sales after a nearly yearlong slump stemming from a short-lived lawsuit that caused the chain some queasiness.

Sales at Taco Bell stores open at least a year – an indicator of a restaurant chain's health – rose 6 percent for the first quarter. Its parent company, Yum Brands Inc., on Thursday predicted even more robust sales gains for the Mexican-style chain in the current quarter.

Yum Chief Financial Officer Rick Carucci predicted sales growth in the high single digits or low double digits.

Taco Bell's introduction of Doritos Locos Tacos in early March has been "enormously successful," Carucci told industry analysts Thursday, one day after Yum reported sharply higher first-quarter earnings on the strength of robust overseas sales and a rebound in the overall company's U.S. performance.

Rollout of tacos that use shells made of Nacho Cheese Doritos came late in the first quarter, so their full impact will be felt in the current quarter. Taco Bell expects to introduce Cool Ranch flavored shells later in the year.

Louisville-based Yum also owns KFC and Pizza Hut, which also had sales gains at established stores in the first quarter. Yum's first-quarter operating profit in the U.S. jumped by 27 percent.

Taco Bell accounts for about 60 percent of U.S. profit for Yum, so its slump had put a dent in the company's performance. It was knocked on its heels by the bad publicity generated by a lawsuit early last year that alleged the meat filling served at its restaurants didn't have enough beef to be called that. Taco Bell denounced the claim as false and spent millions to defend its filling and shore up its image.

The suit was dropped about three months after it was filed by an Alabama law firm. But the chain's sales faltered for months afterward.

Now, the California-based chain known for its hip advertising and late-night snacking aimed at young men seems to have its mojo back.

It's expanding its menu and entering the highly competitive breakfast business.

Taco Bell introduced its breakfast menu early this year at about 800 restaurants, mostly in the western U.S. It plans to expand breakfast to 200 more stores in the second half of 2012, Yum Chairman and CEO David C. Novak said Thursday. The chain has said previously that if the launch goes well, it hopes to begin selling breakfast burritos and hash browns at its more than 5,600 locations nationwide by 2014.

The chain also is testing a Cantina Bell line of more upscale foods created by celebrity chef Lorena Garcia.

"We're looking to broaden the appeal of the brand," Novak said. "We think this is going to extend the breadth of the appeal of the brand, make us more mainstream with both male and female target audiences."

The long-term strategy, he said, is to expand Taco Bell's reach in the U.S. and raise the number of U.S. restaurants to 8,000, he said.

"We think we can be a significant new unit developer in the United States as we improve our unit economics," he said.

Meanwhile, Yum continued its fast-paced international expansion in the first quarter, adding 297 new restaurants. It opened 168 in its key China market, a record for the quarter.

Yum expects to open more than 1,500 new international units in 2012, including at least 600 in China, Carucci said.

Strong growth in overseas sales, especially in China, has been a key growth driver for Yum along with rapid restaurant expansion.

Operating profit in China rose 14 percent in the first quarter, adjusted for currency fluctuations. In the international division, which excludes China and India, operating profit rose 9 percent, adjusted for currency fluctuations.

A slowdown in China's economic growth hasn't shown up in Yum's stores, Carucci said.

Besides the rapid expansion, Novak said, the company has strong potential for volume growth at its existing restaurants in China, where KFC is a leading fast-food brand and Pizza Hut has a strong foothold.

Yum's shares fell$1.53, or 2.1 percent, Thursday to close at $71.41.

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  • Taco Bell Doritos Locos Taco

    <strong>The Method:</strong> The one that started it all uses a proprietary taco shell-shaped Doritos chip as its wrapper, and comes swathed in a special cardboard holder to prevent Doritos powder from coating eaters' hands. <strong>The Verdict:</strong> Very positive reviews all around; most agreed that the tacos had been improved by the extra salt and savoriness of the Doritos shell. The biggest complaint was that there wasn't enough Doritos flavor -- it seemed as if the seasoning had been tamped down vis-a-vis the normal chips. To solve this problem, we tried adding more Doritos in the middle of the taco. It didn't help.

  • Cosi Signature Salad

    <strong>The Method:</strong> We tossed crumbled Doritos into Cosi's signature salad, which contains mixed greens, gorgonzola and cranberries. <strong>The Verdict:</strong> Pretty solid! The chips added some much needed saltiness and crunch to what is usually a sweet, mushy salad. On the other hand, the signature Doritos flavor didn't really stand up to the salad's vinaigrette and ingredients; almost any chip would have improved the salad. In the words of one taster, "Since there is blue cheese in the salad, it feels like the two are competing for attention."

  • Chipotle Burrito

    <strong>The Method:</strong> Since we were too bashful to ask our Chipotle assembly line wrapper to crumble the Doritos into the middle of the burrito, we ended up stuffing it ourselves ex post wrappo. <strong>The Verdict:</strong> Funny! But not good-tasting, sadly. One taster said that the pairing was "good texturally," but most agreed that the subtle, natural flavors of a Chipotle burrito clashed with the artificiality of Doritos.

  • Wendy's French Fries

    <strong>The Method:</strong> Grind the chips into a powder, then shake them up with the fries to coat them evenly. <strong>The Verdict:</strong> Possibly the worst of the pairings. One taster compared them to "dry cheese fries," while another noted that, "Ketchup does not go with Doritos." Blech!

  • McDonald's Big Mac

    <strong>The Method:</strong> Added whole Doritos on top of both the burger's beef patties. <strong>The Verdict:</strong> Bravo! Most tasters agreed that this was almost as good a match as Eddard and Catelyn Stark on "Game of Thrones." (Full disclosure: they did not use a "Song of Ice and Fire" analogy to convey their enthusiasm.) One said, "The creamy sauce complements the crunchy texture of the chips," which, another added, "makes it more satisfying, because usually it's one-dimensional."

  • McDonald's Chicken McNuggets

    <strong>The Method:</strong> We stuck Doritos into the McNuggets, as our photographer put it, "like shards of glass." <strong>The Verdict:</strong> These were divisive. Some tasters hated the combo, finding the McNugget flavor and texture overpowering. But others said that dipping the Doritos-adorned nuggets into barbecue sauce made for a revelatory melding of flavors.

  • Subway Spicy Italian Sub

    <strong>The Method:</strong> Lay whole chips right up in the middle of the sub. <strong>The Verdict:</strong> One of the better matches. One taster even called it "delicious," noting that salami and Doritos have mutually beneficial flavor profiles. Another taster, though, quipped that, "This does not taste discernibly different because normally when I eat a Subway sandwich I'm also stuffing Doritos in my face." (It's not clear that this was a criticism.)

  • Dunkin' Donuts Glazed Donuts

    <strong>The Method:</strong> Because we had three donuts, we decided to try a few things... we stuck them in as with the McNuggets, we stuffed them in the middle as with the Big Mac and we sprinkled their crumbs on top as with the Wendy's Fries. <strong>The Verdict:</strong> Another divisive dish. Though one taster praised the Doritos donuts for their "nice cheesecake taste," others picked up artificial, bitter flavors that they said ruined the meld. Everyone thought they LOOKED awesome though!