Yuanting Tang ^1,2 Xia Wang ^1,2* jialing huang ^1,2,3 Yongmei Jiang ^1,2* Fan Yu ^1,2*

• ¹ Medical Laboratory, West China Second University Hospital, Sichuan University, Chengdu, China
• ² Key Laboratory of Birth Defects and Related Diseases of Women and Children, West China Second University Hospital, Sichuan University, Chengdu, Sichuan Province, China
• ³ Department of Clinical Laboratory, Sun Yat-sen Memorial Hospital, Guangzhou, China

Intraamniotic infection is crucial in preterm prelabor rupture of membranes (PPROM)—a clinical condition resulting from the invasion of vaginal opportunistic microbes into the amniotic cavity. While previous studies have suggested potential associations between infection and PPROM, the role of vaginal opportunistic bacteria in PPROM has received limited attention. This study aimed to confirm the vaginal bacterial etiology of PPROM. We investigated vaginal microbiotas using automatic analysis of vaginal discharge, microbiological tests, and 16s rRNA gene high-throughput sequencing. The research findings revealed that the proportion of parabasal epitheliocytes, leukocytes, toxic leukocytes, and bacteria with diameters smaller than 1.5 μm was significantly higher in the PPROM group than in the normal full-term labor (TL) group. The top three vaginal opportunistic bacterial isolates in all participants were 9.47% Escherichia coli, 5.99% Streptococcus agalactiae, and 3.57% Enterococcus faecalis. The bacterial resistance differed, but all the isolates were sensitive to nitrofurantoin. Compared with the vaginal microbiota dysbiosis (VMD) TL (C) group, the VMD PPROM ( P) group demonstrated more operational taxonomic units, a high richness of bacterial taxa, and a different beta-diversity index. Indicator species analysis revealed that Lactobacillus jensenii, Lactobacillus crispatus, and Veillonellaceae bacterium DNF00626 were strongly associated with the C group. Unlike the C group, the indicator bacteria in the P group were Enterococcus faecalis, Escherichia coli, and Streptococcus agalactiae. These findings provide solid evidence that an abnormal vaginal microbiome is a very crucial risk factor closely related to PPROM. There were no unique bacteria in the vaginal microbiota of the PPROM group; however, the relative abundance of bacteria in the abnormal vaginal flora of PPROM pregnancies differed. Antibiotics should be reasonably selected based on drug sensitivity testing. The findings presented in this paper enhance our understanding of Streptococcus agalactiae, Enterococcus faecalis, and Escherichia coli vaginal bacterial etiology of PPROM in Western China.