Flesh-Eating Bacteria Work Together

The study was conducted by Ashok Chopra, professor of microbiology and immunology at the University of Texas Medical Branch at Galveston in partnership with the Federal Drug Administration, CosmosID Inc., the University of Maryland and the Johns Hopkins University. The findings are considered a positive step towards development of life-saving therapeutics to treat patients.

The bacteria Aeromonas hydrophila has been increasingly acknowledged as being responsible for necrotizing fasciitis, a rapidly-progressing skin and muscle tissue infection. The microbe is commonly found in fresh and brackish water, especially during warmer months. The infection can be acquired through cuts and scrapes in the skin.

The bacteria liquefies muscle tissue and can spread to various organs. Severe cases may require amputation of limbs and death could occur, even after aggressive antibiotic treatment.

Researchers studied a human case of necrotizing fasciitis and identified four strains of Aeromonas hydrophila that caused the infection. Three of the strains were closely related but one was different from the others.

Researchers found that the three similar strains produced a toxin called ExoA that is responsible for breaking down muscle tissue, allowing the distinct strain to move to other parts of the body.

“We provided evidence that presence of these multiple strains of Aeromonas hydrophila significantly influenced disease progression and outcome, more so than if only individual strains had been involved” said Chopra. “These four strains could be differentiated by using advanced laboratory technology but not by routine clinical procedures. What we found was that although mice were infected with all four strains, only one of the strains spread to the inner organs, namely the spleen and liver.”

This discovery could alter the way medical researchers think about this and other bacterial diseases that are commonly thought to be caused by a single species of bacterium.

New technology can now be used to discover infections caused by a mixture of bacterial strains of the same species and may well revolutionize clinical microbiology, directing physicians towards improved treatment options, said Chopra.

This study was the first time scientists were able to determine the role that the ExoA toxin produced by the three similar strains of the bacteria plays in the infection process. Chopra said the plan is to extend analysis of these strains of Aeromonas hydrophila to find ways to prevent or lessen the toxin’s ability to break down muscle tissue.