The Alteration of Intrauterine Microbiota in Chronic Endometritis Patients Based on 16s rRNA sequencing Analysis

Background: Chronic endometritis (CE) is a disease of continuous and subtle inflammation occurred in the endometrial stromal area, which is often asymptomatic or present with non-specific clinical symptoms. Methods This study investigated the composition and distribution of the intrauterine microbiota of 71 patients who underwent hysteroscopy during the routine clinical inspection of infertility. Among them, patients who diagnosed as chronic endometritis (CE) were allocated into CE group (n = 29) and others into non-CE group (n = 42). There was no significant difference in average age between the two groups. Uterine flushing fluid were collected by the self-developed cervical trocar uterine cavity sampler and performed 16S rRNA gene sequencing. Results The alpha diversity in CE group was significantly higher than that in non-CE group (P < 0.05). Firmicutes were the dominant phylum in the non-CE group (72.23%), while its abundance was much lower in CE group (49.92%), but there was no statistical difference between the two groups. The abundances of Actinobacteriota and Cyanobacteria in CE group were significantly higher than in non-CE group (P < 0.05). At genus level, the abundance of Lactobacillus dominated in all samples, which presented lower abundance in CE group (40.88%) than in non-CE group (64.22%). Correspondingly, the abundance of non- Lactobacillus was higher in CE group, among which Pseudomonas and Cutibacterium increased significantly (P < 0.01). Moreover, compared with the non-CE group, the pathways involved arginine and proline metabolism (P = 0.048) and retinol metabolism (P = 0.049) were significantly enriched in CE group, while the metabolism of lipid (P = 0.028) and prenyltransferases (P = 0.046) were significantly decreased in CE group. Conclusions In conclusion, certain microbial community was colonized in the uterine cavity, with Lactobacillus as the dominant genera. The structure and distribution of intrauterine microbiota in CE group were different from non-CE group by showing lower abundance of Lactobacillus , and significantly higher abundance of Pseudomonas and Cutibacterium . As a result, the microbial metabolism was also altered in CE groups. This study elaborated the alteration of intrauterine microbiota in the CE patients, which would improve the diagnosis rate of CE and guiding the selection of antibiotic treatment for CE patients.