The plates
were incubated at 37 C for 5e7 days in anaerobic chamber (Bactron,
Oregon, USA) with 90% N2, 5% CO2, 5% H2. Well isolated
colonies were transferred to BHI agar supplemented with 0.5%
yeast extract and 1% glucose (supplemented BHI) and incubated at
37 C for 3e5 days. P. acnes was identified on the basis of colony
characteristic, Gram-stain, catalase test, indole test, nitrate reduction
test, gelatinase test, and carbohydrate fermentation test.
P. acnes DMST 14916 was included as a reference strain. The
cultures were stored in glycerol broth at 20 C until use.