Abstract: 【Abstract】 Objective To compare the phylotypes of Staphylococcus epidermidis（SE） in skin lesions of acne vulgaris patients versus hair follicles of healthy people, and to analyze their roles in the pathogenesis of acne vulgaris. Methods A cross-sectional study was conducted from August 2022 to August 2023. Patients with moderate acne vulgaris, as well as healthy volunteers, were enrolled from the Department of Dermatology, Renji Hospital, School of Medicine, Shanghai Jiaotong University. SE strains were isolated from the pustules of acne vulgaris patients and hair follicles of healthy volunteers. Housekeeping genes were amplified by PCR. Sequencing and multilocus sequence typing were performed to compare the phylotypes and genetic relationships of strains from different sources. Results The acne group consisted of 28 patients （10 males and 18 females） with the age being 22.6 ± 2.6 years, while the healthy group consisted of 19 volunteers （7 males and 12 females） with the age being 22.4 ± 0.96 years. There were no significant differences in age or gender ratio between the two groups （both P > 0.05）. The positive rates of SE in the samples of the acne group and the healthy group were 60.71% （17/28） and 73.68% （14/19）, respectively, with no significant difference between the two groups （P = 0.53）. The 144 SE strains from the healthy group could be divided into 10 sequence types （STs）, and the most common ST was ST35 （8 cases）, followed by ST73 （4 cases）, ST193 （2 cases）, ST59 （2 cases） and ST540 （2 cases）; 190 SE strains from the acne group could be divided into 16 STs, and the most common STs were ST59 （6 cases） and ST73 （6 cases）, followed by ST802 （3 cases）, ST130 （3 cases） and ST35 （2 cases）. The positive rate of ST35 was significantly lower in the acne group than in the healthy group （P = 0.018）, while there were no significant differences in the positive rates of other STs between the two groups （all P > 0.05）. The evolutionary tree analysis showed that the SE strains were mainly distributed in 3 branches. Most of the SE strains from the healthy group belonged to clade A. The proportion of SE strains in clade A （M［Q］） was significantly lower in the acne group （25% ［85%］） than in the healthy group （100% ［33.33%］, P = 0.025）, while the proportion of SE strains in clade B was significantly higher in the acne group （14.29% ［89.17%］） than in the healthy group （0［0］, U = 62, P = 0.010）, and there was no significant difference in the proportion of SE strains in clade D between the acne group （0 ［57.14%］） and healthy group （0［4.17%］, P = 0.420）. Conclusion The phylotypes of SE strains differed between acne vulgaris patients and healthy controls, possibly associated with the occurrence and development of acne vulgaris.

Key words: Acne vulgaris, Staphylococcus epidermidis, Hair follicle, Microbial consortia, Genotyping techniques, Multilocus sequence typing