Abstract
BackgroundPropionibacterium acnes and Staphylococcus epidermidis live in close proximity on human skin, and both bacterial species can be isolated from normal and acne vulgaris-affected skin sites. The antagonistic interactions between the two species are poorly understood, as well as the potential significance of bacterial interferences for the skin microbiota. Here, we performed simultaneous antagonism assays to detect inhibitory activities between multiple isolates of the two species. Selected strains were sequenced to identify the genomic basis of their antimicrobial phenotypes.ResultsFirst, we screened 77 P. acnes strains isolated from healthy and acne-affected skin, and representing all known phylogenetic clades (I, II, and III), for their antimicrobial activities against 12 S. epidermidis isolates. One particular phylogroup (I-2) exhibited a higher antimicrobial activity than other P. acnes phylogroups. All genomes of type I-2 strains carry an island encoding the biosynthesis of a thiopeptide with possible antimicrobial activity against S. epidermidis.Second, 20 S. epidermidis isolates were examined for inhibitory activity against 25 P. acnes strains. The majority of S. epidermidis strains were able to inhibit P. acnes. Genomes of S. epidermidis strains with strong, medium and no inhibitory activities against P. acnes were sequenced. Genome comparison underlined the diversity of S. epidermidis and detected multiple clade- or strain-specific mobile genetic elements encoding a variety of functions important in antibiotic and stress resistance, biofilm formation and interbacterial competition, including bacteriocins such as epidermin. One isolate with an extraordinary antimicrobial activity against P. acnes harbors a functional ESAT-6 secretion system that might be involved in the antimicrobial activity against P. acnes via the secretion of polymorphic toxins.ConclusionsTaken together, our study suggests that interspecies interactions could potentially jeopardize balances in the skin microbiota. In particular, S. epidermidis strains possess an arsenal of different mechanisms to inhibit P. acnes. However, if such interactions are relevant in skin disorders such as acne vulgaris remains questionable, since no difference in the antimicrobial activity against, or the sensitivity towards S. epidermidis could be detected between health- and acne-associated strains of P. acnes.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-016-2489-5) contains supplementary material, which is available to authorized users.
Highlights
Propionibacterium acnes and Staphylococcus epidermidis live in close proximity on human skin, and both bacterial species can be isolated from normal and acne vulgaris-affected skin sites
Selection of bacterial strains and principal methodology Bacterial isolates, 77 and 24 strains for P. acnes and S. epidermidis, respectively, were previously obtained by swab sampling from human skin of acne patients and healthy individuals [12]
In the first set of experiments, the antimicrobial activity of P. acnes against S. epidermidis was investigated: strains of S. epidermidis were suspended on the agar surface, representing the indicator strains, and P. acnes was added as stab culture
Summary
Propionibacterium acnes and Staphylococcus epidermidis live in close proximity on human skin, and both bacterial species can be isolated from normal and acne vulgaris-affected skin sites. The interaction between S. epidermidis and P. acnes and its relevance for skin health and disease of the host is largely unknown. This microbial interplay, for instance mediated through molecules involved in intercellular competition or communication, may have an impact on the fine balance of the skin ecosystem. A disturbed balance (dysbiosis) can impact skin health and might initiate or support the events that lead to skin disorders [9] One of such disorders is acne vulgaris, a multifactorial disease of pilosebaceous units of the skin that affects adolescents [10]. Microorganisms have been associated with this disease, in particular P. acnes, and it has been reported that S. epidermidis and P. acnes can be isolated together from acne-affected sebaceous follicles [11]
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