Analysis of hair follicle microbiota in non-lesional areas of patients with moderate-to-severe acne vulgaris: a single-center cross-sectional study

Objective·To study the differences in the structure and load of hair follicle microbiota in non-lesional areas among patients with moderate-to-severe acne vulgaris and healthy individuals, and to explore the relationship between microorganisms and the severity of acne vulgaris.Method·A cross-sectional study was used. Patients with moderate or severe acne vulgaris (referred to as acne) and healthy volunteers who visited the Department of Dermatology, Renji Hospital, Shanghai Jiao Tong University School of Medicine, from August 2022 to August 2023. 16S rRNA high-throughput sequencing and quantitative real-time polymerase chain reaction (qPCR) were performed on the follicular contents from the non-lesional areas of the faces of patients with moderate or severe acne and healthy volunteers to analyze the diversity, species composition, and microbial load differences in hair follicle bacteria in patients with different severity of acne.Results·Ten patients with moderate acne, eleven patients with severe acne, and eleven healthy volunteers were included. There were no statistically differences in general data such as age and gender ratio among the three groups. Bacterial α-diversity was significantly lower in both the moderate and severe acne groups compared to the healthy group (P=0.020, P=0.013). The principal coordinates analysis (PCoA) plot showed that the sample distribution of the healthy group was relatively concentrated, with small differences within the group, and the distribution of samples in the moderate and severe acne groups exhibited a certain trend but was relatively scattered, with differences between the groups. There were differences in the trend distribution of the three sample groups, and there were differences in the microbial community structure between the groups. The results of similarity analysis showed significant differences in β-diversity and low similarity in species composition between the healthy and moderate acne groups (P=0.027) and between the healthy and severe acne groups (P=0.017), and high species similarity between the moderate acne and severe acne groups (P=0.160). The dominant bacterial groups at the phylum level were Actinobacteria, Firmicutes, Proteobacteria, and Bacteroidetes. At the genus level, the dominant bacteria in the healthy group were Propionibacterium and unclassified Actinomycetales, and the dominant bacteria in both acne groups were Staphylococcus and Propionibacterium. Compared to the healthy group, the relative abundance of Staphylococcus species in the hair follicles in non-lesional areas of the moderate and severe acne groups was significantly increased (P=0.010, P=0.019). Compared with the healthy control group, the hair follicle microbiota load in non-lesional areas of both the moderate and severe acne groups was significantly increased (both P=0.001). Compared with the moderate acne group, the bacterial load in the hair follicle samples of the severe acne group was significantly increased (P=0.017).Conclusion·The microbial community structure of hair follicles in non-lesional areas of patients with moderate or severe acne is different from that of healthy individuals, and the microbial diversity in the acne group is significantly reduced. The relative abundance of Staphylococcus species in the hair follicles in non-lesional areas of the moderate or severe acne groups is significantly increased compared to the healthy group. As the severity of acne increases, the bacterial load in hair follicles in non-lesional areas significantly increases. This research suggests that the occurrence and severity of acne may be related to the community structure and load of hair follicle microbiota.