Differential susceptibility of Propionibacterium acnes, P. granulosum and P. avidum to free fatty acids.

The susceptibility of 98 Propionibacterium acnes, P. granulosum and P. avidum strains isolated from acne cases and appropriate reference strains to decanoic, dodecanoic, octadeca-9,12 dienoic, and octadeca-9,12,15 trienoic acids was investigated using minimal inhibitory concentration estimation by an agar dilution techique. The tested acids showed their relative antibacterial activity in the following order: C18:3 delta 9,12,15 greater than C18:2 delta 9,12 greater than C12:0 greater than C10:0 Differences between minimal inhibitory concentration values for P. acnes, and P. avidum versus P. granulosum strains were demonstrated in the cases of octadeca-9,12 dienoic, and octadeca-9,12,15 trienoic acids.