SIOUX CITY, Iowa — Margaret Lamkin doesn’t visit her grandchildren much anymore. She never flies. She avoids wearing dresses. And she worries about infections and odors.

Three years ago, at age 87, Lamkin was forced to wear a colostomy bag for the rest of her life after a virulent meat-borne pathogen destroyed her large colon and nearly killed her.

What made her so sick? A medium-rare steak she ate nine days earlier at an Applebee’s restaurant.

Lamkin, like most consumers today, didn’t know she had ordered a steak that had been run through a mechanical tenderizer. In a lawsuit, Lamkin said her steak came from National Steak Processors Inc., which claimed it got the contaminated meat from a U.S. plant run by Brazilian-based JBS — the biggest beef packer in the world.

“You trust people, trust that nothing is going to happen,” said Lamkin, who feels lucky to be alive at 90, “but they (beef companies) are mass-producing this and shoveling it into us.”

The Kansas City Star investigated what the industry calls “bladed” or “needled” beef and found the process exposes Americans to a higher risk of E. coli poisoning than cuts of meat that have not been tenderized.

The process has been around for decades, but while exact figures are difficult to come by, USDA surveys show that more than 90 percent of beef producers are now using it.

Mechanically tenderized meat is increasingly found in grocery stores, and a vast amount is sold to family-style restaurants, hotels and group homes.

The American Meat Institute, an industry lobbying group, has defended the product as safe, but institute officials recently said they can’t comment further until they see the results of a pending risk assessment by the meat safety division of the U.S. Department of Agriculture.

Although blading and injecting marinades into meat add value for the beef industry, that also can drive pathogens — including the E. coli O157:H7 that destroyed Lamkin’s colon — deeper into the meat.

If it isn’t cooked sufficiently, people can get sick. Or die.

There have been several USDA recalls of the product since at least 2000, and a Canadian recall in October included mechanically tenderized steaks imported into the United States, but it’s not clear how many people were sickened.

In a 2010 letter to the USDA, the American Meat Institute noted eight recalls between 2000 to 2009 that identified mechanically tenderized and marinaded steaks as the culprit. Those recalls sickened at least 100 people.

But food safety advocates suspect the incidence of illness is much higher.

An estimate by the Center for Science in the Public Interest, an advocacy group, suggests that mechanically tenderized beef could have been the source of as many as 100 outbreaks of E. coli and other illnesses in the United States in recent years. Those cases affected more than 3,100 people who ate contaminated meat at wedding receptions, churches, banquet facilities, restaurants and schools, the center said.

But that’s just one of the key findings from The Star’s investigation, which examined Big Beef’s processing methods, the use of drugs in cattle and the hazards they can pose for human health.

The Star examined the largest beef packers, including the big four — Tyson Foods of Arkansas, Cargill Meat Solutions of Wichita, Kan., National Beef of Kansas City, Mo., and JBS USA Beef of Greeley, Colo. — as well as the network of feedlots, processing plants, animal drug companies and lobbyists who make up the behemoth known as Big Beef.

What The Star found is an increasingly concentrated industry that mass-produces beef at high speeds in mega-factories that dot the Midwest, where Kansas City serves as the “buckle” of the beef belt. It’s a factory food process churning out cheaper, and some say tougher, cuts of meat that can lead to illness and death. The Star’s other key findings:

- Large beef plants, based on volume alone, contribute disproportionately to the incidence of meat-borne pathogens.

- Big Beef and other processors are co-mingling ground beef from many different cattle, some from outside the United States, adding to the difficulty for health officials to track contaminated products to their source. The industry also has resisted labeling some products, including mechanically tenderized meat, to warn consumers and restaurants to cook it thoroughly.

- Big Beef is injecting billions of dollars of growth hormones and antibiotics into cattle, partly to fatten them quickly for market. But many experts believe that years of overuse and misuse of such drugs contributes to antibiotic-resistant pathogens in humans, meaning illnesses once treated with a regimen of antibiotics are much harder to control.

- Big Beef is using its political pull, public relations campaigns and the supportive science it sponsors to influence federal dietary guidelines and recast steaks and burgers as health foods people can eat every day. It even persuaded the American Heart Association to certify beef as “heart healthy.”

CRITICS: BIG BEEF BRINGS BIG RISKS

Thanks in large part to the Midwest’s grassy plains and ample row crops, the United States produces 26 billion pounds of beef a year from 34 million cattle, more than any other country.

Four of the seven largest beef slaughterhouses — each capable of killing 6,000 head a day — are in Kansas, which leads the nation in meat processing.

The big slaughterhouses are among the last vestiges of old-line American manufacturing, except that they take things apart instead of putting them together. Meat slaughter and processing employs 260,000 people, and Big Beef’s highly efficient plants supply a large share of those jobs in the Midwest.

As a result, despite recent price hikes, beef costs less in the United States than anywhere in the world. It has become America’s crude oil — in high demand worldwide, including faraway lands where a newly minted middle class is acquiring a taste for more expensive protein.

But some independent ranchers, members of Congress and food safety advocates question the wisdom of processing so much beef at such speeds, arguing that “factory food” is more likely to trigger pathogen outbreaks.

Their reasoning: When processing speed and volumes rise, so do the chances for contamination to be introduced and spread widely from its source to other meat inside the plant and at other plants that process it further. In fact, most of the lawsuits that Seattle attorney Bill Marler has filed against the meat industry — winning $250 million in judgments on behalf of children who suffered kidney failure by eating bad hamburger — were against big packing plants, where he said “the problem begins.”

E. coli O157:H7 is a potentially deadly bacterium that can cause bloody diarrhea, dehydration and, in severe cases, kidney failure. The very young, seniors and people with weak immune systems are most at risk. A recent lawsuit against National Steak and JBS noted that there are an estimated 73,480 illnesses linked to E. coli O157:H7 infections each year in the United States, leading to 2,168 hospitalizations and 61 deaths.

USDA data analyzed by The Star show that large plants have had higher rates of positive E. coli tests than smaller plants. Federal meat safety officials said the latest data show those differences are disappearing.

But they acknowledged that the volume of meat a plant produces is a key issue. A USDA study published in March showed that from 2007 through 2011, E. coli positives at very small plants resulted in only 465,000 pounds of contaminated beef. A slightly lower rate of positive tests at large plants, however, produced more than 51 million pounds of contaminated beef.

Regardless, USDA officials and other experts agree that most E. coli generally originates at larger slaughter plants, where pathogen-laden manure is a bigger problem because that’s where cattle are coming in from the feedlots.

Federal inspection records obtained by The Star under the federal Freedom of Information Act include hundreds of references to fecal contamination problems at four of the largest beef slaughter plants in Kansas, Nebraska and Colorado. For example, at Tyson’s Dakota City, Neb., beef plant, inspectors noted: “massive fecal contamination; multiple carcasses with varying degrees of fecal contamination; periods of very significant fecal, ingesta and abscess contamination.”

Another federal inspector at Tyson found “a piece of trimmed fat approximately 14 inches long with feces the length of it,” and another noted, “fecal contamination ... was so great ... couldn’t keep up.”

But Tyson officials said such reports only provide a “snapshot of beef production.” The company said it has added two full-time safety technicians at the plant, as well as additional workers, to assess carcasses and make sure fecal contamination is eliminated.

USDA and beef industry officials point out that E. coli illnesses have dropped dramatically in recent years, although the Food Safety and Inspection Service cautioned that no “consistent trend” has emerged in recalls of contaminated beef.

LABELING IS VOLUNTARY

More and more, the beef industry is using machines with automated, double-edged blades to cut through muscle fibers and connective tissue to penetrate tougher cuts of meat.

Hollow needles are sometimes used to inject flavorings, or what the industry calls “digestive agents.” Marinades also may be added to meat, which can add to contamination risks.

Surveys of beef producers by the USDA found that most use mechanical tenderization to improve quality. A large percentage of mechanically tenderized meat — the industry produces at least 50 million pounds a month — winds up in family-style restaurants, hotels, hospitals and group homes.

For Big Beef, mechanically tenderized meat is all about bigger profits, according to food safety advocates. However, the beef industry doesn’t widely publicize the process, and some food safety advocates say the reason is such labeling can lead to sales declines.

The American Meat Institute, citing a 2008 USDA study, has maintained that the risk of illness from E. coli O157:H7 in such products “is not significantly higher.”

But a more recent study published last year in the Journal of Food Protection found that bladed and marinated steaks were two to four times riskier than those that had not been mechanically tenderized.

The American Meat Institute has said that blade-tenderized steaks are just as safe as other steaks if “the meat is properly cooked.” The institute also found that if researchers had allowed the steaks to “rest” and continue cooking for an additional three minutes before taking their samples, those remaining “fortuitous survivors” may have been killed.

Some experts say Big Beef is relying on the process more and more because beef is getting tougher.

Changes in animal feeding practices are causing cattle to come to market sooner, said David Theno, a beef industry consultant and leading food safety expert. Those animals often “have less marbling and may be less tender than animals that spend more time in feedlots,” he explained.

Theno, who helped the Jack in the Box restaurant chain reform its practices after an E. coli O157:H7 outbreak in the 1990s, said problems with mechanically tenderized meat can arise because many consumers don’t want their steaks overcooked. But failing to heat them sufficiently can allow pathogens to survive.

USDA research also discovered an ominous phenomenon in mechanically tenderized and marinated meat. The 2011 Journal of Food Protection article warned that cooking highly contaminated bladed steaks on a gas grill — even at 160 degrees like hamburger — might not kill all E. coli bacteria.

Those remaining living pathogens, ironically called “fortuitous survivors” by scientists, survive because of cold spots in the meat.

Such risks have been identified “for quite some time,” said Carlota Medus, principal epidemiologist for Minnesota’s health department.

“We have seen it (mechanically tenderized meat) as a vehicle for outbreaks since 2003,” she said. “It’s not as risky as ground beef, but it is definitely riskier than an intact steak.”

Food-safety advocates point out that most consumers, restaurants and grocery stores don’t know they’re buying bladed meat and therefore don’t know it should be cooked more thoroughly. The Safe Food Coalition “strongly believes” such products pose “a serious and unnecessary threat to public health.”

For years, the USDA has urged the industry to voluntarily label such products but found in 2008 that few beef plants were doing so. Costco is among stores which do label such products as being bladed. Those labels advise consumers that “for your safety USDA recommends cooking to a minimum temperature of 160 degrees.”

Not labeling mechanically tenderized beef jeopardizes consumers and puts health officials at a disadvantage if there’s an outbreak of E. coli, experts said.

For now, the USDA recommends cooking all beef steaks — mechanically tenderized or not — to a minimum internal temperature of 145 degrees, then letting them sit for 3 minutes.