Sebum has antibacterial properties due to sapienic acid and oleic acid according to this article on sebum. According to the same article, desaturation of fatty acids increases acne development. Another article, also suggests that the free fatty acids contribute to the antibacterial properties of sebum.
How does Propionibacterium acnes survive the antibacterial effects of sebum? Does it lack the enzymes to break down lipids in the sebum to form the antibacterial free fatty acids?
Also why are certain acne medications are so effective simply by inhibiting sebum production? Is sebum actually metabolic fuel for Propionibacterium acnes?