Innovation

The science behind flesh-eating bacteria and its cure

Learn answers to common questions about necrotizing fasciitis, the infection that has taken Aimee Copeland's leg and may claim her life.

Written by Laura Shin, Contributor May 15, 2012 at 8:00 p.m. PT

In case you haven't heard of Aimee Copeland, she is the 24-year-old fighting off a life-threatening infection of flesh-eating bacteria.

The eco-psychology grad student caught the gruesome affliction last week after falling from a homemade zipline into Georgia's Little Tallapoosa River May 1st and sustaining a deep gash to her left calf that required 22 staples to stitch up.

Within three days, a bacteria called Aeromonas hydrophila, common in warm climates and fresh water, had caused an infection called necrotizing fasciitis in the leg. In order to prevent the infection from spreading further, doctors have amputated most of her left leg, part of her abdomen and may amputate her other foot and part of her hands, though they hope to save her palms so she can someday use prosthetic fingers.

Below are answers to some common questions about her condition and how it can be prevented and cured.

What is necrotizing fasciitis and what causes it?

Necrotizing fasciitis is a rare but severe bacterial infection of soft tissues that causes them to die. It attacks muscles, the connective tissue covering muscle, and skin.

The way such an infection starts is when certain types of bacteria enter the body, usually through a cut or scrape. That bacteria begins to grow inside the body, releasing toxins that kill tissue. The bacteria then enters the blood, spreading throughout the body.

Several types of bacteria can cause necrotizing fasciitis. While Copeland's was caused by Aeromonas hydrophila, that's one of the rarer causes of necrotizing fasciitis. The bacteria that most commonly causes the infection is Streptococcus pyogenes, known in lay terms as “flesh-eating bacteria." Staph and combinations of different bacteria can also cause it.

However, these bacteria are not deadly all the time. What makes them dangerous is an oxygen-free environment. “If I went swimming in the same water and dunked my head, nothing would happen to me,” William Schaffner, an infectious-disease specialist at Vanderbilt University Medical Center in Nashville,told The Daily Beast. "This is not a bug that can get on the surface and burrow in. Something has to give it access to those deep tissues and that was the problem here. She had that injury into which the water was splashed. This is a bug that is essentially harmless except when it finds itself in the wrong place.”

And when it does find itself in that "wrong place," it "can switch its metabolism so that it can also function in an oxygen-poor environment," Schaffnertold USA Today.

Why does it take time to detect?

Because the infection takes root so deep, a victim and his/her doctors may not realize that necrotizing fasciitis is there until it has already spread.

The patient may feel pain in the early stages, but the wound will display no visible clues such as redness, swelling or discharge. Even more deceptively, there will be no fever, which typically indicates infection. So until the diagnosis is made, the infection can spread.

“It’s one of the few true infectious-disease emergencies where an hour can make a huge difference,” Otto Yang, an infectious-diseases physician at UCLA’s David Geffen School of Medicine, told The Daily Beast.

How is it cured and prevented?

Because of necrotizing fasciitis's high mortality rate (upward of 60% for infections caused by Aeromonas hydrophila, according to a 2010 report in Clinical Microbiology Reviews), immediate and drastic measures are necessary.

They include treating the wound, powerful antibiotics, and surgery to drain the sore and remove dead and infected tissue. If the disease has spread, aggressive surgery, including amputation, is often necessary, to take out not just the dead tissue but also healthy tissue where the infection may already be working microscopically. This type of approach goes against conventional surgical training, which teaches that viable tissue must be preserved. "It’s not unusual for surgeons to have to go back a second or third time to keep up with and get ahead of the infection,” Schaffner told The Daily Beast.

Often, patients need skin grafts after the infection goes away, in order to help heal the skin.

Dr. Amy Horneman, a specialist in Aeromonas hydrophila who is chief of microbiology and molecular diagnostics at the Baltimore Medical Center of the Veterans Affairs Maryland Health Care System, has not treated Copeland but has been studying the bacteria for 30 years.

To prevent necrotizing fasciitis infections caused by the bacteria, she has been waging a campaign to get doctors and the general public to remember to think of the bacteria whenever they are dealing with a water-related wound.

As with many diseases, the best cure is prevention, and the key to prevention is education. She told The Los Angeles Times that common antibiotics such as Ciprofloxacin, Bactrim, SXT and Septra can easily take care of the bacteria before the infection sets in -- as long as they are administered in time.

via: The Daily Beast, USA Today, CBS News, Los Angeles Times

photo: Official site for Aimee Copeland