Minocycline effectively reduces acid producted by Propionibacterium granulosum.

We studied the effects of minocycline on Propionibacterium granulosum. P. granulosum lipase activity was detected from acne lesions. Production of propionic and butyric acids by P. granulosum was well suppressed by all tested media with added minocycline; the higher the concentration of minocycline in the medium, the less of these acids was produced. It appeared that the decrease in these acids due to minocycline was greater in P. granulosum than in P. acnes. Although the influence of P. granulosum on acne lesions might be feebler than that of P. acnes, we should not neglect its presence. More research is needed to elucidate the relationship between the two species in acne lesions.