Skin bacteria a new source of antimicrobials?

Lindsay Kalan (right) and MSc student Jordana Ferro examine a dish containing skin-associated bacteria. Photo courtesy McMaster University News

The human skin microbiome may be an untapped source of new antibiotics and other antimicrobial agents, researchers at McMaster University report.

In a study published in the journal Nature Communications, the investigators swabbed more than 30 volunteers at eight body sites representing distinct microenvironments—including the neck, nostrils, back, arms, umbilicus, and toes—and assembled 968 unique strains of bacteria, among them four previously unknown species. The resulting library, dubbed the Epithelial Isolate Collection, or EPIC is, according to the researchers, the largest and most diverse collection of skin-associated microbes ever assembled.

When they systematically exposed the library to a panel of more than 20 human pathogens—ranging from bacteria such as E. coli and S. aureus to fungi such as Cryptococcus and multidrug-resistant C. auris—many of the skin bacteria inhibited pathogen growth in laboratory assays. Three of the four new species produced chemicals that were especially effective at deterring disease-causing fungi.

"These new species of bacteria are what we're calling 'fungal specialists,'" said Lindsay Kalan in a press release. "They can inhibit several different kinds of pathogenic fungi, including those that are otherwise drug-resistant." She is an associate professor in McMaster's Department of Biochemistry and Biomedical Sciences and associate director of the Michael G. DeGroote Institute for Infectious Disease Research.

Genomic analysis revealed substantial uncharacterized biosynthetic potential: across all the skin bacteria studied, only 4% of the gene clusters traditionally responsible for antimicrobial production had been previously characterized, indicating that the remainder could encode novel molecules.

"What we found was a tremendous amount of novelty," Kalan said.

The reported laboratory findings do not establish clinical efficacy. Kalan's team is now working to understand the medicinal potential of the most intriguing new molecules and is exploring whether the bacteria themselves could one day be harnessed as skin probiotics.

The research was supported in part by the National Institutes of Health, the Weston Family Foundation and the Canada Research Chairs Program.