By Daniel Cressey

Guidelines for medical teams responding to catastrophes such as the Haiti earthquake may be causing doctors to miss a crucial set of deadly bacteria.

According to an Israeli Defense Forces (IDF) rapid-response team, a large proportion of the wounds treated at their field hospital in Haiti were infected with Gram-negative pathogens. These bacteria are largely ignored in current recommendations on drug treatment for disaster victims.

Staining with the dye crystal violet is widely used to differentiate bacteria into two types -- Gram-positive and Gram-negative -- in a procedure developed in the nineteenth century by Hans Christian Gram. Crucially, drugs that are effective against one type of bacteria may not work against the other.

Guidelines from the World Health Organization (WHO) and from the US Centers for Disease Control and Prevention (CDC) in Atlanta, Georgia, recommend treating injured patients with antimicrobials that target Gram-positive bacteria, as these strains are the most common cause of wound infections. But what is the case in hospitals in the West doesn't necessarily hold for the extreme conditions following a disaster.

"Skin and soft-tissue injuries are usually associated with Gram-positive pathogens and thus the previous guidelines seemed reasonable," says Ian Miskin, a doctor with the Clalit Health Services organization based in Jerusalem, and who was part of the rapid-response team. "However, after lying in the rubble for hours to days after an earthquake it appears that the pathogens causing wound infections were Gram-negative -- possibly due to wound contamination with fecal material."

In the immediate aftermath of the earthquake that devastated Haiti in January, the IDF set up a 72-bed mobile hospital. Over ten days the hospital admitted 737 victims of the disaster.

Miskin's team set up an on-site microbiology laboratory which analysed cultures taken from patients with infected wounds. They found that 77% of 46 wounds analysed contained multiple types of microbe, with 89% showing Gram-negative pathogens.

These Gram-negative bacteria were also mostly resistant to antimicrobials recommended by the CDC and WHO disaster-response guidelines, the researchers note in a letter in this week's New England Journal of Medicine.

Miskin, lead author of the letter, adds, "If teams responding to future earthquakes do not equip themselves with appropriate antibiotics they may be unable to treat the wound infections resulting from the earthquake damage."

He stresses the vital importance of on-site microbiology, which allows doctors to tailor their treatments to the local pathogens found in victims.

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Previous studies have indicated that Gram-negative bacteria are present in wounds in most disaster victims. However, these studies focused on referral hospitals and patients who had already received antibiotic treatment. So it was always possible that the bacteria were present as a result of hospital contamination or of the initial antibiotic treatment wiping out the Gram-positive bacteria.

Andrew Lee, a doctor and researcher in disaster response and international health at the University of Sheffield, told Nature that Miskin's report is "a timely piece and of considerable implications for current medical practice in disaster settings".

However, he warns that, although microbiological tests carried out in the field are hugely valuable, they are logistically very difficult. An alternative solution is that doctors could treat first with a short course of penicillins, which are effective against Gram-positive infections, then follow up with drugs that target Gram-negative bacteria if the initial treatment is ineffective.

Richard Murphy, a medical advisor to Médecins Sans Frontières (MSF), says that his organization did stress the importance of Gram-negative infections in its guidance to Haiti responders, but says that there needs to be a wider appreciation of the problem. "In soft tissue and bone infections in warm countries we've known for some time that Gram-negative organisms can be as important or more important than Gram-positive infections."

The WHO was unable to comment before this article was published. The CDC said that it does not comment on non-CDC authored articles.