Isolation and Characterization of P. acnes Strains

P. acnes strain ATCC 6919 was obtained from American Type Culture Collections (Manassas, VA). Clinical isolates were obtained from Biodefense and Emerging Infections Research Resources Repository (BEI Resources) and from nasal skin microcomedones from patients attending the Division of Dermatology outpatient clinic at UCLA, after signed written informed consent as approved by the Institutional Review Board at UCLA in accordance with the Declaration of Helsinki Principles. The level of endotoxin contaminating the P. acnes was quantified with a Limulus Amoebocyte Lysate assay (BioWhittaker, Radnor, PA) and found to be <0.1 ng ml⁻¹. P. acnes cultures were grown as previously described (Agak et al., 2014 (link)). P. acnes strains and clinical isolates used in the study are summarized in Table 1.