Characterisation of Cutibacterium acnes phylotypes in acne and in vivo exploratory evaluation of Myrtacine®.

OBJECTIVE: Our main objective was to compare Cutibacterium acnes (C. acnes) skin colonisation in patients with mild to moderate acne versus healthy controls and secondly, to evaluate a Myrtacine® -based cream on C. acnes total population and antibioresistant Cutibacteria in patients with acne. METHODS: In 60 acne patients (Global Acne Severity Scale, GEA grades 2-3), of mean age 20 [15-30] years and in 24 age- and sex- matched healthy controls, forehead strips samplings were performed for microbiological analysis of comedones by colony forming unit (CFU) counts of global C. acnes and erythromycin (EryR) or clindamycin-resistant (ClnR) populations of Cutibacterium and determination of phylotypes by MALTI-TOF. Clinical evaluations of acne patients (GEA, lesion count, porphyrin fluorescence) were performed at baseline and after 56 days of twice-daily application of a Myrtacine® -based cream. RESULTS: We first showed (i) high and similar levels of C. acnes colonisation in superficial pilosebaceous follicles and detection of EryR and ClnR strains in both acne and control groups; (ii) different repartition of phylotypes in acne patients versus healthy control, with a predominance of phylotype IA in acne patients and a link between phylotype IA and erythromycin resistance. Besides, after treatment with the Myrtacine® -based cream in acne patients, there was no change in C. acnes total load, but a significant decrease of EryR Cutibacteria, reduced porphyrin production by C. acnes, a decrease in acne severity (GEA), associated with reduced retentional and inflammatory lesions. CONCLUSION: Cutibacterium acnes colonisation was not significantly different in acne versus control groups. Phylotype IA was predominant in acne patient and in EryR C. acnes. A Myrtacine® -based cream significantly reduced the level of EryR Cutibacteria in vivo and improved acne lesions.

Cutibacterium acnes (Propionibacterium acnes) and acne vulgaris: a brief look at the latest updates.

While the commensal bacterium Propionibacterium acnes (P. acnes) is involved in the maintenance of a healthy skin, it can also act as an opportunistic pathogen in acne vulgaris. The latest findings on P. acnes shed light on the critical role of a tight equilibrium between members of its phylotypes and within the skin microbiota in the development of this skin disease. Indeed, contrary to what was previously thought, proliferation of P. acnes is not the trigger of acne as patients with acne do not harbour more P. acnes in follicles than normal individuals. Instead, the loss of the skin microbial diversity together with the activation of the innate immunity might lead to this chronic inflammatory condition. This review provides results of the most recent biochemical and genomic investigations that led to the new taxonomic classification of P. acnes renamed Cutibacterium acnes (C. acnes), and to the better characterisation of its phylogenetic cluster groups. Moreover, the latest data on the role of C. acnes and its different phylotypes in acne are presented, providing an overview of the factors that could participate in the virulence and in the antimicrobial resistance of acne-associated strains. Overall, this emerging key information offers new perspectives in the treatment of acne, with future innovative strategies focusing on C. acnes biofilms and/or on its acne-associated phylotypes.

Sessile Legionella pneumophila is able to grow on surfaces and generate structured monospecies biofilms.

Currently, models for studying Legionella pneumophila biofilm formation rely on multi-species biofilms with low reproducibility or on growth in rich medium, where planktonic growth is unavoidable. The present study describes a new medium adapted to the growth of L. pneumophila monospecies biofilms in vitro. A microplate model was used to test several media. After incubation for 6 days in a specific biofilm broth not supporting planktonic growth, biofilms consisted of 5.36 ± 0.40 log (cfu cm(-2)) or 5.34 ± 0.33 log (gu cm(-2)). The adhered population remained stable for up to 3 weeks after initial inoculation. In situ confocal microscope observations revealed a typical biofilm structure, comprising cell clusters ranging up to approximately 300 µm in height. This model is adapted to growing monospecies L. pneumophila biofilms that are structurally different from biofilms formed in a rich medium. High reproducibility and the absence of other microbial species make this model useful for studying genes involved in biofilm formation.