Introduction
The microbiota of the female genital tract and its role in health and disease has extensively been studied. The vaginal microbiome has been well described both in healthy reproductive-age women (1), and postmenopausal women (2). Various community state types (CST) exist within the vaginal microbiome, and while most states are dominated by lactobacilli, other diverse, non-lactobacilli-based microbiome profiles have been described, sometimes associated with the presence of bacterial vaginosis (BV) (1,3,4).
Together with the well-characterized lower genital tract microbiome, the presence of bacteria in the upper reproductive tract including the uterine cavity,  the placenta, and fallopian tubes, has been more frequently investigated in recent years  (5). Studies examining the presence of bacteria in the fallopian tubes found a diverse microbial environment, albeit in very low quantities (6–8). A study examining the ovarian microbiome found significant differences between cancer patients and healthy controls (9). As these sites are accessible only via a surgical procedure, there is an obvious obstacle in studying and establishing a healthy microbial fingerprint, if one exists
Hydrosalpinx denotes a blocked edematous fallopian tube that is filled with fluid. Tubal blockage and tubal infertility usually result from previous pelvic infection such as pelvic inflammatory disease (PID), but damage to the fallopian tube from previous surgery, endometriosis or adhesions can also result in hydrosalpinx (10,11). The association of hydrosalpinx with decreased pregnancy and implantation rates in in vitro fertilization (IVF) cycles has been widely reported, and value for surgical treatments for tubal disease prior to IVF has been previously established (12).
Microbiome studies examining infertility found different endometrial and vaginal bacterial compositions associated with implantation and pregnancy rates (13) as well as different lactobacilli-dominated vaginal compositions, associated with pregnancy rates in women with unexplained infertility (14). A recent meta-analysis also pointed to the association between BV, a marker of vaginal dysbiosis, with tubal factor infertility (15). BV has also been shown to be associated with increased risk for sexually transmitted infections  (16) pelvic inflammatory disease (17), and preterm labor (18). However, the association between the vaginal and fallopian tube microbiomes and their relation to hydrosalpinx has yet to be elucidated.
In this study, we aim to describe the vaginal microbiome of women undergoing salpingectomy for hydrosalpinx and compare it with those undergoing salpingectomy for various other indications. Furthermore, we analyze the microbiome of the resected fallopian tubes and its association with hydrosalpinx.