Since the discovery of the first antibiotic, penicillin, we have been involved in a fierce competition with bacteria. We invent or discover an antibiotic, bacteria adapt by generating enzymes to degrade the antibiotic, so we have to produce yet more new antibiotics. To win this race, we desperately need to develop alternative weapons—either non-antibiotics or novel antibiotics to kill harmful bacteria by new mechanisms. If we cannot find better weapons soon, the World Health Organization (WHO) predicts that antibiotic-resistant bacterial infections could kill more people than cancer .
One solution is to identify and employ natural enemies of harmful bacteria. Commensal bacteria, the human-friendly bacteria often living in our noses, guts, and other parts of our bodies, may be good candidates. While harmful bacteria infect us and cause diseases, commensal bacteria can sometimes outgrow or kill many other harmful bacteria strains, thus providing a potential powerful weapon for host defense. Recently, scientists identified one such strain of nasal commensal bacteria named Staphylococcus lugdunensis . It produces a unique small protein-based chemical compound called lugdunin, which can effectively kill the pathogenic Staphylococcus aureus that frequently infect our skin. When applied to the skin of infected mice, lugdunin greatly reduced the population of S. aureus. More surprisingly, lugdunin quickly eliminated S. aureus and prevented them from developing resistance for at least a month, while S. aureus grew resistant to a traditional antibiotic within only a few days. It’s possible that lugdunin, with its unique structure compared to most traditional antibiotics, targets different biological pathways in S. aureus. Thus, lugdunin represents a novel type of natural antibiotic that can potently kill infectious bacteria with low risk of antibiotic resistance. This finding also identifies commensal bacteria as an under-explored antibiotic resource, which beckons us to unveil more secrets that evolution has sealed in commensal bacteria.
PhD Candidate, Molecular Biology Interdepartmental Doctoral Program (MBIDP), UCLA
 “Antimicrobial resistance: global report on surveillance 2014.” (2014) World Health Organization. Web.
 Zipperer A., Konnerth M.C., Laux C., et al. Human commensals producing a novel antibiotic impair pathogen colonization. (2016). Nature DOI: 10.1038/nature18634