Nasal cavities are an underappreciated body part, but they are a gold mine for University of Tübingen microbiologist Bernhard Krismer, who explores the bacterial interactions in this ecosystem. 

     A laboratory glass container holds a white substance.
Researchers identified a novel antimicrobial compound called epifadin, which requires special storage conditions due to its unstable nature. 
Jonas Ritz, University of Tübingen

Among the nose residents, the potentially pathogenic bacteria Staphylococcus aureus (S. aureus) piqued Krismer’s attention. S. aureus does not colonize people’s nares equally, and the presence of natural bacterial competitors could help explain these differences.1 

Recently, Krismer and his colleagues discovered a new antimicrobial synthesized by a strain of the nasal commensal Staphylococcus epidermidis (S. epidermidis).2 The molecule eliminated S. aureus, revealing a novel strategy that S. epidermidis may use to outcompete S. aureus in the nares.

In their quest for nasal antimicrobials, Krismer and his team first isolated bacteria from nasal swabs from healthy volunteers. They found that one of the isolates, a strain of S. epidermidis, produced an unknown compound, epifadin, which inhibited S. aureus proliferation in vitro and in nasal colonization experiments in rats.

After confirming that epifadin lysed S. aureus cells in vitro, the researchers set out to characterize the molecule. When they attempted to purify the antimicrobial using a strategy that had worked with another antimicrobial compound, they failed.3 “[Epifadin] is highly active; it's very potent. But unfortunately, it’s very unstable,” noted Krismer. 

After two years, Krismer’s team successfully purified and solved epifadin’s chemical structure, revealing a chimeric peptide-polyene-tetramic acid structure, which is unlike any previously described antimicrobial compound. 

Identifying a short-lived antimicrobial is an unexpected discovery according to Kim Lewis, a molecular microbiologist at Northeastern University who was not involved in the research. “That is contrary to what we generally know about production of antimicrobials that tend to be stable,” he explained. 

Next, Krismer plans to keep exploring the nasal microbiota to uncover novel molecules that mediate bacterial interactions. “There is more out there,” he said. 

References

  1. van Belkum A, et al. J Infect Dis. 2009;199(12):1820-1826
  2. Torres Salazar BO, et al. Nat Microbiol. 2024;9(1):200-213
  3. Zipperer A, et al. Nature. 2016;535(7613):511-516.