Cutibacterium modestum sp. nov., isolated from meibum of human meibomian glands, and emended descriptions of Cutibacterium granulosum and Cutibacterium namnetense.

An anaerobic and aerotolerant bacterium, strain M12T, was isolated from the meibum of inflamed human meibomian glands. Cells of the strain was Gram-stain-positive, non-spore-forming and non-motile rods. Growth on trypticase soy agar plates supplemented with 5 % sheep blood was fastest at 30-37 °C under anaerobic conditions. The 16S rRNA gene sequence of the strain revealed that it belongs to the genus Cutibacterium with a 98.0 % similarity value to the closest species, Cutibacterium acnes. Genome analysis of the strain with type strains of the other Cutibacterium species resulted in digital DNA-DNA hybridization values of 32.3-22.3% and average nucleotide identity (OrthoANI) values of 86.7-73.6 %. Biochemical and physiological analyses using API rapid ID 32A and API Coryne kits revealed relatively low reactivity of the strain compared with C. acnes and Cutibacterium namnetense. The most abundant major cellular fatty acid was iso-C15 : 0. Fermentation end-products from glucose were propionate, lactate, succinate and acetate. The diagnostic diamino acid of the peptidoglycan was meso-diaminopimelic acid. Major menaquinones were MK-9(H4), MK-9(H2) and MK-9. The major peaks of the MALDI-TOF mass spectrometry spectrum were at 3493, 3712, 6986 and 7424 Da. The DNA G+C content was 59.9 mol%. Based on these findings, we propose a novel species, Cutibacterium modestum. The type strain of C. modestum is M12T (=JCM 33380T=DSM 109769T). On the basis of further genomic analysis, we also provide emended descriptions of Cutibacterium granulosum (Prévot 1938) Scholz and Kilian 2016 and Cutibacterium namnetense (Aubin et al. 2016) Nouioui et al. 2018.