Abstract
Acne vulgaris is the most common dermatological disorder worldwide affecting more than 80% of adolescents and young adults with a global prevalence of 231 million cases in 2019. The involvement of the skin microbiome disbalance in the pathophysiology of acne is recognized, especially regarding the relative abundance and diversity of Propionibacterium acnes a well-known dominant human skin commensal. Biofilms, where bacteria are embedded into a protective polymeric extracellular matrix, are the most prevalent life style for microorganisms. P. acnes and its biofilm-forming ability is believed to be a contributing factor in the development of acne vulgaris, the persistence of the opportunistic pathogen and antibiotic therapy failures. Degradation of the extracellular matrix is one of the strategies used by bacteria to disperse the biofilm of competitors. In this study, we report the identification of an endogenous extracellular nuclease, BmdE, secreted by Propionibacterium granulosum able to degrade P. acnes biofilm both in vivo and in vitro. This, to our knowledge, may represent a novel competitive mechanism between two closely related species in the skin. Antibiotics targeting P. acnes have been the mainstay in acne treatment. Extensive and long-term use of antibiotics has led to the selection and spread of resistant bacteria. The extracellular DNase BmdE may represent a new bio-therapeutical strategy to combat P. acnes biofilm in acne vulgaris.
Highlights
Biofilm formation is a surviving strategy contributing to the composition and long-term stability of the microbial populations (Rendueles and Ghigo, 2015; Flemming et al, 2016)
A co-culture of P. granulosum as well as cell‐free supernatant (CFS) of P. granulosum with a six-days old P. acnes biofilm resulted in total dispersion of the biofilm after 48 hours (Figure 1A)
Results show that r-BmdE treatment does not impact P. acnes viability since the bacteria released from biofilm could be regrown on agar plate supporting results obtained with the viability assay kit
Summary
Biofilm formation is a surviving strategy contributing to the composition and long-term stability of the microbial populations (Rendueles and Ghigo, 2015; Flemming et al, 2016). Secretion of nucleases has been described mostly as a strategy used by pathogens to evade the host immune system (Sharma et al, 2019). Whether endogenous matrix-degrading nucleases have any role in the setting of inter-species competition within biofilms is unknown. The skin commensal Propionibacterium granulosum, while colonizing the same PSU as P. acnes, is commonly seen as a separate community (Jahns et al, 2015) implying a possible existence of a competitive mechanism. P. acnes biofilms are dominant in PSU (Jahns et al, 2012; Jahns et al, 2013a) and we hypothesized that a biofilm-degrading mechanism may be beneficial for P. granulosum colonization. We further speculated that this mechanism should be executed through a component secreted by P. granulosum
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