BOSTON - In the biggest criminal case ever brought in the United States over contaminated medicine, 14 former owners or employees of a Massachusetts pharmacy were charged Wednesday in connection with a 2012 meningitis outbreak that killed 64 people.

The nationwide outbreak was traced to tainted drug injections manufactured by the now-closed New England Compounding Center of Framingham.

Barry Cadden, a cofounder of the business, and Glenn Adam Chin, a pharmacist who was in charge of the sterile room, were hit with the most serious charges, accused in a federal racketeering indictment of causing the deaths of 25 patients in seven states by "acting in wanton and willful disregard of the likelihood" of death or great bodily harm.

Among other things, Cadden, Chin, and others are accused of using expired ingredients, failing to properly sterilize drugs, and failing to test them to make sure they were pure. The other defendants were charged with such crimes as fraud and interstate sale of adulterated drugs.

U.S. Attorney Carmen Ortiz said that the compounding pharmacy was "filthy" and failed to comply with even basic health standards and that employees knew it. For example, she said, they falsified logs about when labs were cleaned.

"Production and profit were prioritized over safety," Ortiz said.

More than 750 people in 20 states were sickened - about half of them with a rare fungal form of meningitis, the rest with joint or spinal infections - and 64 died. The steroids given were for medical purposes, not for bodybuilding; most patients received the injections for back pain.

In reaction to the outbreak, Congress last year increased federal oversight of so-called compounding pharmacies like New England center, which custom-mix medications in bulk and supply them directly to hospitals and doctors.

Linda Nedroscik of Howell, Mich., said that her husband, John, survived the tainted injection, but that the 64-year-old "still struggles, has nightmares."

"It's hard to say it's a relief," she said of the indictment, "because it doesn't change anything for us in our physical lives. But it takes a burden off emotionally."

Chin's lawyer, Stephen Weymouth, said he was stunned that prosecutors charged his client with second-degree murder under the racketeering law.

"He feels hugely remorseful for everything that's happened - for the injuries and the deaths - but he never intended to cause harm to anybody," Weymouth said. "It seems to be a bit of an overreach."