Adaptation of acneic and non acneic strains of Cutibacterium acnes to sebum‐like environment

Abstract

Cutibacterium acnes, former Proprionibacterium acnes, is a heterogeneous species including acneic bacteria such as the RT4 strain, and commensal bacteria such as the RT6 strain. These strains have been characterized by metagenomic analysis but their physiology was not investigated until now. Bacteria were grown in different media, brain heart infusion medium (BHI), reinforced clostridial medium (RCM), and in sebum like medium (SLM) specifically designed to reproduce the lipid rich environment of the sebaceous gland. Whereas the RT4 acneic strain showed maximal growth in SLM and lower growth in RCM and BHI, the RT6 non acneic strain was growing preferentially in RCM and marginally in SLM. These differences were correlated with the lipophilic surface of the RT4 strain and to the more polar surface of the RT6 strain. Both strains also showed marked differences in biofilm formation activity which was maximal for the RT4 strain in BHI and for the RT6 strain in SLM. However, cytotoxicity of both strains on HaCaT keratinocytes remained identical and limited. The RT4 acneic strain showed higher inflammatory potential than the RT6 non acneic strain, but the growth medium was without significant influence. Both bacteria were also capable to stimulate β‐defensine 2 secretion by keratinocytes but no influence of the bacterial growth conditions was observed. Comparative proteomics analysis was performed by nano LC‐MS/MS and revealed that whereas the RT4 strain only expressed triacylglycerol lipase, the principal C. acnes virulence factor, when it was grown in SLM, the RT6 strain expressed another virulence factor, the CAMP factor, exclusively when it was grown in BHI and RCM. This study demonstrates the key influence of growth conditions on virulence expression by C. acnesand suggest that acneic and non acneic strains are related to different environmental niches.

Acne and Stress: Impact of Catecholamines on Cutibacterium acnes

“…This does not exclude a potential role of catecholamines in C. acnes inflammatory activity, as other host molecules are likely necessary for full expression of this potential. These results are similar to those obtained using HaCat keratinocytes (27) and SZ95 sebocytes grow in a complex sebum-like medium which is particularly favorable to C. acnes . Thus, the low cytotoxicity and inflammatory potential of both strains of C. acnes suggest that this bacterium behaves more as a skin commensal than as an opportunistic pathogen, at least in the absence of stimulation by host factors.…”

“…Colonies were transferred into sterile conical 15-mL tubes (Falcon) filled to maximal capacity with reinforced clostridial medium (RCM) and grown at 37°C. As previously demonstrated, RCM was better adapted for the culture of these strains (27). Bacteria were collected after 72 h (stationary phase) and sub-cultured at 37°C under anoxic conditions in RCM supplemented, or not, with 10 −6 M epinephrine or norepinephrine (Sigma).…”

“…In addition, the stimulation of biofilm formation induced by epinephrine was lower for the RT6 strain than the RT4 strain (153 vs. 60%) and was only observed when the cells were grown on a hydrophobic surface, such as polystyrene. The RT4 acneic strain is adapted to a hydrophobic environment and is strictly anaerobic, whereas the RT6 non-acneic strain requires a more polar medium and is more aerotolerant (27). The RT4 acneic strain has been postulated to originate from the sebaceous compartment, whereas the RT6 non-acneic strain has been postulated to come from the skin surface and upper part of the hair follicle.…”

“…As recently shown, the matrix of C. acnes contains highly diverse molecules, which can affect the viability of eukaryotic cells (40), and biofilm matrix is frequently considered itself to be a virulence factor (41). In addition, C. acnes virulence factor expression can be modulated by the microenvironment (27) and generally requires the contribution of host molecules, such as acid sphingomyelinase (42). However, C. acnes is not a true pathogen but more a cause of inflammation (38).…”

The Skin Microbiome: A New Actor in Inflammatory Acne

“…Vitamin B12 supplementation further increases C. acnes production of porphyrins [ 25 ]. Finally, C. acnes types IA and IB were found to induce greater levels of production of the human antimicrobial peptide (AMP), β-defensin 2 (hBD2), from cultured sebocytes, and displayed higher levels of lipase activity than a type II isolate [ 26 ].…”