The role of staphylococcal bacteriocins in nasal competition

Bacteriocins are antimicrobial toxins produced by bacteria to defend and invade territories by killing unrelated strains and species. Understanding if bacteriocins shape natural populations is important for understanding the evolution of antimicrobial resistance and identifying novel antimicrobials for clinical use. Staphylococcus aureus is an opportunistic pathogen that asymptomatically colonises the nasal cavity of 1 in 3 healthy adults. S. aureus is known to produce many different bacteriocins, however we are yet to understand the extent to which they mediate the establishment of nasal populations. Here, we test the importance of bacteriocins in driving colonisation success, by screening S. aureus antimicrobial inhibition against otherS. aureus strains and three commensal species that commonly co-inhabit the nasal cavity. We use a longitudinally sampled collection of 173S. aureusnasal isolates from 14 participants over 90-months to track within-individual population changes over time. We found that 8% of allS. aureus isolates produced bacteriocins active against other species, but that between-strain bacteriocin inhibition inS. aureus was very rare, observed by only 0.5% of isolates. Therefore, while there is no evidence that intraspecific competition drives colonisation success in the nasal cavity, interspecific competition is more likely to influence strain and species dominance.