Materno-fetal and Obstetrics Research Unit

Bacteria and other microorganisms colonize most of the human body. They are not passive commensals but have a profound influence on the host homeostasis and play a significant role at multiple levels, including protection against pathogens, maturation of the immune system, metabolic pathways, vitamin synthesis and others. It is thus not surprising that a disbalance or dysbiosis of the microbiota has been associated with several adverse outcomes.

The human genital tract is not an exception to bacterial colonization. While the existence of a vaginal microbiota has been well established, other genital sites have been considered sterile environments with a general assumption that bacterial presence is a pathological situation. However, recent studies identified specific patterns of microbiota colonizing these sites, but their role remains poorly explored.

Dysbiosis of the genital microbiota has been linked to the impairment of reproduction and adverse pregnancy outcomes such as preterm birth. Despite this, studies on the impact of bacteria remain scarce and, when available, are descriptive analyses. In particular, more effort is needed towards understanding host-microbial interactions at the molecular level and how microbiota could be shaped to restore homeostasis.

Our research interests span between the early stages of microbial colonisation of the newborns, the impact of the microbiota on preterm births, the interplay between partners’ microbiota and its possible role in infertility.

Figure 1: different ongoing microbiota projects in our research group

Related publications:

• Home or hospital birth: the neonatal microbiota perspective. Stojanov M., Das S., Odent M., Engel P., Baud D., 2022/04. The Lancet. Microbe, 3 (4) pp. e247.
• Bacterial Colonization of the Female Upper Genital Tract. Peric A., Weiss J., Vulliemoz N., Baud D., Stojanov M., 2019/07/11. International journal of molecular sciences, 20 (14).
• Sperm Microbiota and Its Impact on Semen Parameters. Baud D., Pattaroni C., Vulliemoz N., Castella V., Marsland BJ, Stojanov M., 2019/02/12. Frontiers in Microbiology, 10 pp. 1-9.

Once specific bacteria are identified in observational studies (such as 16S rRNA-based community analyses), their positive or negative impact should be further explored and confirmed using animal models or in vitro models of infection/colonization.

C. trachomatis is the most commonly reported sexually transmitted bacterial infection worldwide, with more than 100 million new cases annually, 90% being asymptomatic. However, infection may translate into significant complications such as miscarriage, preterm birth, neonatal pneumonia, tubal infertility, ectopic pregnancy, pelvic inflammatory disease (PID), blindness and urethritis.

Our group is currently focused on the initial steps of chlamydial infection, which, despite the notoriety of this bacterium, remains understudied. Our main goal is to identify all the cellular receptors exploited by this pathogen to penetrate into host cells.

Related publication:

• Chlamydial polymorphic membrane proteins: regulation, function and potential vaccine candidates. Vasilevsky S, Stojanov M, Greub G and Baud D. Virulence. 2016 Jan; 7(1): 11–22.

Figure 5: Attachment of C. trachomatis on cell surface during the initial steps of the infection.

Waddlia chondrophila, an emerging pathogen associated with miscarriages

Approximately 25% of women will experience at least one miscarriage during their life. Despite a large number of possible investigations, a cause of the miscarriage is identified in less than 50% of the cases. Intracellular bacteria, which are not routinely investigated in clinical practice, might represent possible agents of miscarriages of unknown etiology. Listeria monocytogenes, Chlamydia trachomatis and Coxiella burnetii are known intracellular bacteria associated with adverse pregnancy outcome. Recently, several studies identified Waddlia chondrophila, an emerging intracellular bacterium belonging to the order of Chlamydiales, to be strongly associated with adverse pregnancy outcomes both in women and animals. W. chondrophila positive serologies as well as PCR and immunohistochemistry (both in the genital tract and placenta) were more likely to be present in women with miscarriages.

Our group is currently investigating:

• The mode of infection of W. chondrophila infection during pregnancy;
• The immune response against W. chondrophila in women who experienced miscarriage compared to women with uneventful pregnancies;
• The immunological mechanisms related to W. chondrophila induced miscarriage.

Related publications:

• Chlamydia trachomatis and chlamydia-like bacteria: new enemies of human pregnancies. Ammerdorffer A, Stojanov M, Greub G, Baud D. Curr Opin Infect Dis. 2017 Jun;30(3):289-296.
• Waddlia chondrophila and Male Infertility. Baud D., Vulliemoz N., Zapata MVM, Greub G., Vouga M., Stojanov M., 2020/01/17. Microorganisms, 8 (1).
• Impact of Waddlia chondrophila infection on pregnancy in the mouse. Baud D., Ammerdorffer A., Buffe Y., Vouga M., Greub G., Stojanov M., 2020/01. New microbes and new infections, 33 p. 100619.
• Waddlia chondrophila induces systemic infection, organ pathology, and elicits Th1-associated humoral immunity in a murine model of genital infection. Vasilevsky S., Gyger J., Piersigilli A., Pilloux L., Greub G., Stojanov M., Baud D., 2015. Frontiers In Cellular and Infection Microbiology, 5 p. 76.
• Role of Waddlia chondrophila placental infection in miscarriage. Baud D., Goy G., Osterheld M.C., Croxatto A., Borel N., Vial Y., Pospischil A., Greub G., 2014. Emerging Infectious Diseases, 20 (3) pp. 460-464.