Cathelicidin-BF, a snake cathelicidin-derived antimicrobial peptide, could be an excellent therapeutic agent for acne vulgaris.

Cathelicidins are a family of antimicrobial peptides acting as multifunctional effector molecules in innate immunity. Cathelicidin-BF has been purified from the snake venoms of Bungarus fasciatus and it is the first identified cathelicidin antimicrobial peptide in reptiles. In this study, cathelicidin-BF was found exerting strong antibacterial activities against Propionibacterium acnes. Its minimal inhibitory concentration against two strains of P. acnes was 4.7 µg/ml. Cathelicidin-BF also effectively killed other microorganisms including Staphylococcus epidermidis, which was possible pathogen for acne vulgaris. Cathelicidin-BF significantly inhibited pro-inflammatory factors secretion in human monocytic cells and P. acnes-induced O2.- production of human HaCaT keratinocyte cells. Observed by scanning electron microscopy, the surfaces of the treated pathogens underwent obvious morphological changes compared with the untreated controls, suggesting that this antimicrobial peptide exerts its action by disrupting membranes of microorganisms. The efficacy of cathelicidin-BF gel topical administering was evaluated in experimental mice skin colonization model. In vivo anti-inflammatory effects of cathelicidin-BF were confirmed by relieving P. acnes-induced mice ear swelling and granulomatous inflammation. The anti-inflammatory effects combined with potent antimicrobial activities and O2.- production inhibition activities of cathelicidin-BF indicate its potential as a novel therapeutic option for acne vulgaris.

Investigation of antibacterial activity of rosemary essential oil against Propionibacterium acnes with atomic force microscopy.

In the present study, the antibacterial activity of rosemary (Rosmarinus officinalis L. Labiatae) essential oil against Propionibacterium acnes (P. acnes) was observed with atomic force microscopy (AFM). The MIC (minimal inhibitory concentration) value of rosemary essential oil against P.acnes was 0.56 mg/mL. Significant changes in morphology and size of P. acnes were observed by atomic force microscopy (AFM) in response to essential oil treatment. The essential oil first attached to the surface of P. acnes at low concentration, the width and height of the bacterial body became larger, whereas the length did not change considerably. With increasing concentration of the essential oil, the bacterial bodies were severely damaged. The length, width and height were all reduced, when the concentration was increased up to 64xMIC, the length, width and height were reduced by 42.56%, 92.00% and 41.58%, respectively. Furthermore, treated bacteria lost their native shape, the cell wall desquamated, and the cytoplasm leaked out of the bacterial body, finally leading to bacterial death. With the increasing time at MIC, the bacteria length was reduced at 8 h, the width and height gradually became smaller, the shape of the cell became distorted, and finally led to cell wall damage and bacterial death at 8 h. In conclusion, the AFM investigation of morphology and size of P. ACNES treated with rosemary essential oil represents a powerful technique, which can generally be applied to reveal the biological changing mechanisms of bacteria induced by antibacterial agents at the nanometer level.