Iranian Journal of Medical Microbiology

Background and Objective: The microbial flora colonizing the pilosebaceous unit plays a crucial role in maintaining skin health and homeostasis. This study aimed to isolate, identify, and evaluate the biofilm-forming capacity of bacterial strains derived from the pilosebaceous follicles of healthy human facial skin.
Methods: Facial sebum samples were collected from 15 healthy volunteers. Bacterial strains were isolated and cultured under anaerobic conditions. Species identification was performed using 16S rRNA gene sequencing. The biofilm-forming ability of the isolates was quantified using the crystal violet staining assay.
Results: A total of 22 bacterial strains were isolated, predominantly Gram-positive, nonmotile, and morphologically characterized as rod-shaped (20/22) or coccoid (2/22). Colonies appeared opaque and white, with diameters ranging from 0.5 to 1.5 mm. Biochemical profiling showed that most isolates were catalase positive (18/22) and gelatinase positive (20/22), while the majority were oxidase negative (18/22). Three isolates exhibited lipase activity, and eight demonstrated hemolysin production. Based on 16S rRNA gene sequencing, Cutibacterium was identified as the dominant genus, with C. acnes accounting for 68% of the isolates. Biofilm assays revealed variability among C. acnes strains, with isolates Hn15-2, Hn4, and Hn13 displaying strong biofilm-forming capacity.
Conclusion: Healthy human facial skin harbors a diverse bacterial community, predominantly composed of Cutibacterium acnes. Notably, several C. acnes isolates demonstrated substantial biofilm-forming ability, suggesting potential implications for skin microbiome stability and pathogenicity.