Abstract
Background
Although described as a commensal bacterium with low pathogenicity, Cutibacterium acnes involvement has been reported in many clinical entities: infections associated with devices, such as shoulder prosthetic joint infections, osteosynthesis, breast implants or cerebrospinal fluid shunts. Various studies show that C. acnes grows as a biofilm, contributing to its persistence by allowing its escape from the action of the immune system and antibiotics.
Purpose
Our aim was to assess the activity of different active substances (erythromycin, clindamycin, doxycycline and Myrtacine®) on eight different well-characterized C. acnes strains after growth in biofilm mode.
Methods
Eight susceptible strains of C. acnes were selected for this study, including two reference strains (ATCC6919 and ATCC11827) and six clinical strains. All C. acnes strains were studied using two different methods to study the biofilm production at different time points: the BioFilm Ring Test® technique (early stages of adhesion) and the Crystal Violet (CV) method (mature biofilm). In a second step, the impact of different active substances (erythromycin, clindamycin, doxycycline and Myrtacine®) was studied. For the CV technique, two types of tests were performed: preventive tests (addition of active substances and bacteria at the same time) and curative challenge tests (addition of active substances on a biofilm already formed after 48h). Transmission electron microscopy was performed to investigate the morphology modifications.
Results
C. acnes isolates from phylotypes IA1 and IA2, seem to produce more mature biofilm in the first stages of adhesion than other phylotypes. Curative assays were performed to evaluate the efficacy of antibiotics and Myrtacine® on mature biofilm. Significant efficacy of Myrtacine® at 0.03% was observed for C. acnes strains. Moreover, the combination of Myrtacine® and doxycycline appears to decrease the total biofilm biomass. The effect of doxycycline as a preventive measure was minimal. On the contrary, a similar use of Myrtacine® as early as 0.001% showed significant efficacy with a significant decrease in total biofilm biomass for all C. acnes strains. Transmission electron microscopy revealed a significantly decreased biofilm growth in treated bacteria with Myrtacine® compared to untreated bacteria. Moreover, the total number of bacteria decreased as the concentration of Myrtacine® increased suggesting also an antimicrobial effect.
Conclusion
These results confirm the difference in biofilm producing ability depending on C. acnes phylotypes. These results suggest that Myrtacine® may be a promising alternative antibacterial and anti-biofilm agent like peroxide de benzoyle to prevent shoulder prosthetic joint infection involving planktonic and biofilm C. acnes.
