All about flesh eating bacteria

The 24 year old graduate student Aimee Copeland fell when a homemade zip line over the Little Tallapoosa River broke. She hit the rocks below, suffering deep cuts that became infected with flesh eating bacteria. And the horror began, with doctors forced to amputate both feet, both hands, all of one leg, and part of her body, in an effort to save her life. When told they would remove her hands she reportedly looked up and mouthed the words “Let’s do this”, appreciating that her purple hands would have to go.

So, what is flesh eating bacteria? The condition can be caused by many different kinds of bacteria, including Streptococcus pyogenes, Staphylococcus aureus and Clostridium perfringens. In the case of Aimee the culprit appears to be Aeromonas hydrophila, found in warm climates and fresh or brackish water. Like the antibiotic resistant strains of Staphylococcus aureus (MRSA), it is resistant to most antibiotics. It produces a toxin (poison) called Aerolysin Cytotoxic Enterotoxin that damages tissue.

How do you catch it? It can infect cuts, as was the case for Aimee, or you can even get it from a bruise (about one third of cases), and sometimes there is no evidence of an injury at all. You can also get it through foods, including seafood, meats and some vegetables.

The bacteria that cause it are fairly common, so the question is why do some people get it and others not? People with compromised immune systems are susceptible, as you might expect. But there is also increasing evidence that some people are genetically predisposed to get certain infections, even if their immune systems are otherwise perfectly fine. For some reason their immune systems are particularly prone to invasion by certain strains of bacteria. It also appears that the bacteria can make toxins that disable the immune system.

How do you treat it? The Aeromonas bacteria encode a protein called beta lactamase that degrades penicillin and the penicillin derivative antibiotics. Despite antibiotic resistance most strains will respond to so-called third generation agents. The other treatment is surgical removal of the most infected areas (surgical debridement).

What are the symptoms? The first symptom is usually pain at the site of a wound. Then the pain gets worse and the tissue around the wound swells and can change in color. As the infection spreads there are flu like symptoms with fever, nausea and diarrhea. It is important to get treatment early. Death can result within 24 hours, and even with high-dose antibiotic treatment about 25% of patients die.

The technical term for flesh eating bacteria is necrotizing fasciitis, which is a fancy way of saying dying tissue. It is generally relatively rare, with about 4 cases per 100,000 people (http://www.bioedonline.org/news/news.cfm?art=1234). So don’t panic, but be careful (Warning: Graphic image of injured leg with flesh eating infection, – Eds)!