In his book “Fast Food Nation,” investigative journalist Eric Schlosser famously wrote of hamburgers, “there is [s**t] in the meat.” Now a Consumer Reports test of 300 packages of ground beef has come to the same conclusion.

Experts at Consumer Reports’ Center for Food Safety and Sustainability bought 300 packages, or 458 pounds, of ground beef from more than 100 stores in 26 cities. They analyzed it for common bacteria that can make people sick. Here’s what they discovered, and what an infectious disease expert and the meat industry have to say.

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Putting ground beef to the test

The researchers tested the equivalent of about 1,800 quarter pounders for five bacteria types commonly found in beef. The headline-grabbing result: All of the samples contained bacteria that reflect contamination with feces. The samples had enterococcus, non toxin-producing E. coli, or both. The bacteria can cause blood infections or urinary tract infections.

One in five samples had C. perfringens, a bacterium responsible for about a million cases of food poisoning in the United States each year.

One in ten contained a strain of S. aureus bacteria capable of producing a toxin that can make you sick even if you cook the burger to the recommended 160 degrees Fahrenheit or more.

Only 1 percent of the samples were positive for salmonella. That may not sound like much, but it could translate to many illnesses and even deaths annually considering how much ground beef Americans consume. In the past year, the researchers say, U.S. consumers bought 4.6 billion pounds of beef, including ground beef.

The researchers recommend buying beef that is sustainably produced rather than conventionally produced, as the sustainably produced samples were less likely to have bacteria overall and less likely to have bacteria resistant to antibiotics. The sustainably produced meat tested came from cows that weren’t given antibiotics, at a minimum. Some were given no antibiotics or other drugs and were also fed organic feed. Conventional samples came from cattle fattened up with grain and soy in feedlots and given antibiotics and other drugs.

Conventional beef was also twice as likely to be contaminated with so-called superbugs, bacteria resistant to three or more classes of antibiotics. That makes the infections they cause nearly impossible to treat.

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The meat industry responds

The findings triggered a strong response from the North American Meat Institute, which includes as its members about 95 percent of the red meat packers in the United States.

"We believe the headline is what they don't report," says Eric Mittenthal, an institute spokesperson. That is, the test results did not find concerning levels of pathogens of most concern to public health in beef, he says.

Specifically, he says, they found no toxin-producing E. coli, a dangerous kind, and just 1 percent of the samples were found to contain with salmonella. That 1 percent, according to Mittenthal, is ''far below USDA performance standards.''

Urvashi Rangan, PhD, director of consumer safety and sustainability for Consumer Reports, responded to SafeBee: “The levels we found don't violate any laws, that is true. But there is a gap between legal requirements and making beef as safe as it can be. So for example, we found 1 percent salmonella in beef, and that sounds low, but that translates to about 23 million pounds of ground beef expected to contain salmonella.” He adds, “General E. coli is a measure of fecal contamination and an indicator for problematic E. coli, too.”

What do doctors say?

The study was designed to test bacteria levels in ground beef, not whether the meat made people sick, notes Aaron Glatt, MD, a spokesperson for the Infectious Diseases Society of America and hospital epidemiologist for the South Nassau Communities Hospital in New York.

Bacteria is everywhere, of course, he says, even on your knife and fork. Pathogens need to be ''in high enough concentrations to make you sick." What concentrations are “high enough” varies from person to person, depending on the state of their health, he says.

Still, of the findings, he says, "It's not an ideal situation." But cooking your burger properly will reduce the risk, he says. Some bacteria can produce a toxin that can't be killed by cooking, as the researchers note, but, says Glatt, cooking beef to 160 degrees or higher can go a long way toward making sure you don’t get sick.

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It's especially important to make sure the burger is cooked through, not grilled to doneness on the outside but raw inside. People with underlying health problems such as a compromised immune system or a lack of stomach acid to kill bacteria need to pay even closer attention to the risks, says Glatt. 

Kathleen Doheny is a Los Angeles journalist specializing in health, behavior and fitness topics.