Mechanistic study of novel antimicrobials for infection prevention and cure

The rise of antibiotic resistance development has increased the need for conventional compounds and unconventional antimicrobials to increase the artillery of medical practitioners in the combat against resistant pathogens. This study aimed in identifying novel synthetic compounds and to determine the mode of action of unconventional antimicrobials known as alpha-helical cationic antimicrobial peptides (AMPs). Initially, we improved the SporeTracker software, used for live-imaging of spore-forming bacteria, resulting in SporeTrackerX. We then established the value of live-imaging analysis and SporeTrackerX in screening of novel synthetic compounds, derived from combinatorial chemistry, using B. subtilis and B. cereus spores. Subsequently, we established the mode of action of AMPs derived from the human thombocidin, TC19 and TC84, and the bactericidal permeability increasing protein (BPI), BP2, using B. subtilis vegetative cells and spores. We found, in vivo, that alpha-helical cationic AMPs cause “membrane leaks” at the site of membrane insertion by altering the organization and fluidity of the membrane. Also for the first time, we show that alpha-helical cationic AMPs target the inner membrane of germinated spores and hint at a potential additional application for AMPs in preventing spore outgrowth after covering the dormant spore-coat.