German researchers say they've found the first evidence of a substance in human sweat that appears to kill several types of common bacteria and yeasts. The substance, a peptide called Dermcidin, is described in the December issue of Nature Immunology.
Lead author Birgit Schittek heads the Laboratory of Dermatologic Oncology at Eberhard-Karls-University in Tübingen. She normally studies the genes that regulate the spread of malignant melanoma.
By chance, her team discovered the Dermcidin gene, which is expressed only by sweat gland cells. They examined it further to determine the gene's function, and found that it had antimicrobial properties.
The researchers found that the peptide produced by Dermcidin killed E. coli, Enterococcus faecalis, Staphylococcus aureus and the yeast Candida albicans.
"It's very efficient -- a very low concentration kills these four microorganisms," says Schittek. "It works as a sort of barrier against microorganisms."
"It's the first peptide which is constantly produced by the skin," she says. "The other antimicrobial peptides, the defensins, are also produced by skin cells, but only after inflammation."
As yet, Schittek doesn't know exactly how Dermcidin kills these bacteria. However, she suspects that it may be linked to the peptide's electrical charge. "Antimicrobial peptides. . . have a positive charge, and most of them kill the bacteria by forming pores in the membrane of the bacteria," she says.
"Our peptide has a negative charge, so it's different from the other antimicrobial peptides. So it might be that there is another mechanism of killing bacteria."
Robert Hancock, director of the Center for Microbial Diseases and Host Defense Research in Vancouver, Canada, says the difference in electrical charge could be important in determining how Dermcidin works.
He points out that peptides tend to exist in families. "It may well be that this will provide us a window to understanding other peptides in other species and human beings," he says.
Schittek says that Dermcidin expression may differ between individuals. "There exist some people who get infectious diseases of the skin more often, like patients with atopic dermatitis," she says. "It might be that they have less of this peptide in their sweat."
In future studies, the researchers also plan to test whether Dermcidin kills viruses and strains of bacteria that have become resistant to conventional antibiotics. Bacteria usually take longer to become resistant to antimicrobial peptides than to antibiotics. If the same is true for Dermcidin, says Schittek, it may be of use as a topical application.
They also hope to determine whether Dermcidin can be used safely to fight infections elsewhere inside the body.
Hancock says that, to date, all of the existing antimicrobial peptides that are progressing towards clinical trials are being developed as topical formulations. "There is a toxicity issue," he says, along with the extreme cost of developing a drug for use elsewhere in the body.
Many questions remain to be answered, cautions Hancock, but he says that the German researchers have taken an essential step.
"Right now, the whole issue of how the body protects itself against daily exposure to microorganisms is a really critical one," says Hancock. "There's a huge potential to develop quite novel therapeutic strategies where you really trying to boost the body's ability to protect against pathogens. This is certainly one significant step towards understanding that."
What To Do
This may provide yet another reason to get a workout.
You can also check out this information on antimicrobial resistance from the Centers for Disease Control and Prevention.