High Frequency and Diversity of Antimicrobial Activities Produced by Nasal Staphylococcus Strains against Bacterial Competitors

Abstract

The human nasal microbiota is highly variable and dynamic often enclosing major pathogens such as Staphylococcus aureus. The potential roles of bacteriocins or other mechanisms allowing certain bacterial clones to prevail in this nutrient-poor habitat have hardly been studied. Of 89 nasal Staphylococcus isolates, unexpectedly, the vast majority (84%) was found to produce antimicrobial substances in particular under habitat-specific stress conditions, such as iron limitation or exposure to hydrogen peroxide. Activity spectra were generally narrow but highly variable with activities against certain nasal members of the Actinobacteria, Proteobacteria, Firmicutes, or several groups of bacteria. Staphylococcus species and many other Firmicutes were insusceptible to most of the compounds. A representative bacteriocin was identified as a nukacin-related peptide whose inactivation reduced the capacity of the producer Staphylococcus epidermidis IVK45 to limit growth of other nasal bacteria. Of note, the bacteriocin genes were found on mobile genetic elements exhibiting signs of extensive horizontal gene transfer and rearrangements. Thus, continuously evolving bacteriocins appear to govern bacterial competition in the human nose and specific bacteriocins may become important agents for eradication of notorious opportunistic pathogens from human microbiota.

Coagulase-Negative Staphylococcal Strain Prevents Staphylococcus aureus Colonization and Skin Infection by Blocking Quorum Sensing

“…The spent media did not inhibit S. aureus growth (Fig. S1), indicating that S. caprae does not produce an antimicrobial agent such as those that have been recently reported in other commensal staphylococci (Janek et al, 2016; Nakatsuji et al, 2017; Zipperer et al, 2016). Next, the S. caprae spent media was subjected to various treatments and tested for impact on an S. aureus agr type I reporter.…”

“…As commensal bacteria colonize a specific niche and compete for resources, extensive interactions occur (Ghoul and Mitri, 2016), and competing bacteria can produce factors that limit S. aureus growth. For commensal CoNS species, it has been observed that S. epidermidis secretes a protease, and S. lugdunensis and other species release antimicrobials, each of which restricts S. aureus colonization (Iwase et al, 2010; Janek et al, 2016; Nakatsuji et al, 2017; Zipperer et al, 2016). These examples illustrate how resident commensal species directly target S. aureus to gain a competitive advantage for resources, thereby limiting pathogenic outgrowth and invasion within shared ecological niches.…”

“…Given that other CoNS make competing AIPs (Fig. 1B and (Canovas et al, 2016)), and the observation that many isolates produce antimicrobials (Janek et al, 2016; Nakatsuji et al, 2017; Zipperer et al, 2016), there is clearly a network of complex, competitive interactions among commensals in the skin environment. Nakatsuji et.…”

“…CoNS are generally non-pathogenic commensals of humans and other animals, and have received less attention in the literature than the more virulent Staphylococcus aureus . However, recent studies have described a number of interactions between CoNS and S. aureus that share similar host niches (Iwase et al, 2010; Janek et al, 2016; Nakatsuji et al, 2017; Sugimoto et al, 2013; Zipperer et al, 2016), demonstrating that these species can compete with S. aureus during colonization and potentially alter its pathogenic behaviour. CoNS - S. aureus interactions are only beginning to be appreciated, and are important for a complete understanding of polymicrobial colonization dynamics.…”

Bacteriocin production: a relatively unharnessed probiotic trait?

“…observed a high frequency of bacteriocin production among nasal Staphylococcus strains with highly variable antimicrobial activity against other nasal members, suggesting a need to inhibit different competitors 48 . The diverse activity spectra of bacteriocins within the nose may facilitate the ability of a bacterial species to dominate the resident populations, suggesting the development of probiotics that could promote a desirable microbiota composition and eliminate pathogens such as S .…”