Flesh-eating bacteria devoured the muscle and skin on the arm of a New Orleans woman after she injected "bath salts," an increasingly popular stimulant drug. Doctors say the infection is unusual, but might become more widespread as more users inject the drug to get high.

When the 34-year-old woman came to the emergency room at the Louisiana Health Sciences Center in August 2011, her right arm was painfully swollen and dotted with a small red puncture wound. Doctors gave her intravenous antibiotics - standard for treating mild skin infections - and her problems gradually disappeared.

But two days later, Dr. Robert Russo, an orthopedic resident at the hospital, said he was puzzled why the woman's infection wasn't getting better quickly. "I asked her about the puncture wound on her arm, and she admitted to using drugs," he said.

The woman told him that she had injected the stimulant-drug known as bath salts at a party the night before she came to the hospital, according to a case report that Russo wrote in the journal Orthopedics.

Things went from bad to worse. The woman's skin began blistering and turned from red to a purplish hue. Doctors decided it was time to operate. When they cut open her forearm, they found dead skin and muscle, the warpath of flesh-eating bacteria. "It spread where you could almost see it moving," he said.

In the time it took doctors to operate further up her arm, the tissue was dying right before their eyes. To stop the infection for good, doctors amputated the woman's arm and right breast.

The woman survived and underwent a few months of rehabilitation. Russo said she was released from the hospital and left the state.

Russo said he's uncertain how the flesh-eating bacteria got into the woman's arm. It could have been lurking on the needle she used or in the bath salts themselves. But he said he worries that the drug's growing popularity means more people will be at risk for infection.

"Just from people using more needles, you could see a rise in these kinds of cases," he said. "And the risks of using this drug, it's not just getting your arm taken off. The drug is crazy."

Bath salts are a powder made of amphetamine-like chemicals, such as methylenedioxypyrovalerone (MPDV), mephedrone and pyrovalerone, according to the National Institute on Drug Abuse. Once sold legally online and in drug paraphernalia stores, users mostly snorted or swallowed it to get high. Recently, injection has become a more popular route, because it delivers the drug's effects faster and more powerfully. The Drug Enforcement Administration made the drug illegal in September.

In light of the drug's growing popularity, Russo said emergency physicians need to be more aware of the drug's effects and look for warning symptoms in their patients.

"It's something new that doctors need to be aware of and start asking their patient's about, because you could end up saving their limb or their life," he said.