The vaginal microbiome and seminal microbiome are both crucial for reproductive and sexual health, influencing fertility, infection risk, and even HPV clearance. One common condition affected by these microbiomes is bacterial vaginosis (BV)—an imbalance in vaginal or seminal bacteria that can lead to discomfort, increased STI susceptibility, and pregnancy complications.

But BV isn’t just about the vaginal microbiome—research suggests that the seminal microbiome also plays a role in its development and persistence. Let’s explore how they interact.

🔬 What is the Vaginal Microbiome?

The vaginal microbiome is a dynamic ecosystem of bacteria, which live in the vagina and maintain vaginal health.

A Healthy Vaginal Microbiome

• Dominated by Lactobacillus species (especially L. crispatus, L. jensenii, L. gasseri).
• Absence or low levels of pathogenic bacteria such as Gardnerella vaginalis, Atopobium vaginae, Prevotella.
• Produces lactic acid, keeping vaginal pH low (~3.5–4.5), which prevents the overgrowth of harmful bacteria.
• Protects against infections like BV, HPV, and other STIs.

An Imbalanced Vaginal Microbiome (BV)

• Decrease in Lactobacillus species and overgrowth of anaerobic bacteria (Gardnerella vaginalis, Atopobium vaginae, Prevotella).
• Vaginal pH rises above 4.5, making it easier for pathogens to thrive.
• Symptoms: Thin, greyish discharge, fishy odor, discomfort, but often asymptomatic.

🔬 What is the Seminal Microbiome?

The seminal microbiome is the community of microorganisms in semen. Just like the vaginal microbiome, it plays a role in reproductive health and infection risk.

A Healthy Seminal Microbiome

• Contains Lactobacillus species or other species that support sperm health and reduce inflammation.
• Helps maintain a balanced immune response, which may protect against infections.

An Imbalanced Seminal Microbiome (Dysbiosis)

• Overgrowth of BV-associated bacteria like Gardnerella, Prevotella, and Mycoplasma.
• High bacterial load.
• Imbalance in microbial diversity – including reduced diversity.
• Can contribute to inflammation, poor sperm health, and a higher risk of passing infections to partners.

🔗 How the Vaginal & Seminal Microbiomes Interact in BV

1️⃣ Unprotected Sex & BV Bacteria Exchange

• Semen microbiota can directly influence vaginal microbiota.
• If a partner’s semen contains BV-associated bacteria, it can disrupt the vaginal microbiome and trigger or prolong BV.
• Studies suggest that men can act as BV reservoirs, leading to recurrent BV in female partners.

2️⃣ pH Disruption from Semen

• Semen has a higher pH (~7.2–8.0) than the vaginal environment.
• Frequent exposure to semen without Lactobacillus support can raise vaginal pH, allowing BV bacteria to thrive.
• In comparison, a healthy vaginal microbiome, with supportive Lactobacillus species, is able to protect better against these changes and maintain a balanced environment.

3️⃣ Inflammation & Immune Response

• A dysbiotic seminal microbiome may increase inflammatory cytokines, weakening the vaginal immune response.
• This may make the vagina more susceptible to BV, STIs, and HPV persistence.

🛡️ How to Maintain a Healthy Microbiome & Prevent BV

For Women

✅ Support vaginal microbiome health with probiotics, prebiotic-rich foods, and a balanced diet.
✅ Prevent imbalance through lifestyle, such as avoid douching or harsh soaps.
✅ Use condoms or microbiome-friendly lubricants to protect against pH disruption.
✅ Get microbiome testing to personalise your vaginal health strategy.

For Men

✅ Support semen microbiome health with probiotics, prebiotic-rich foods, and a balanced diet.
✅ Prevent imbalance through lifestyle, such as avoid smoking or harsh soaps.
✅ Get tested and treated for BV-associated bacteria if a partner has recurrent BV.
✅ Use condoms to reduce the transfer of BV-associated bacteria.

🌿 Bottom Line: A Shared Responsibility for Reproductive Health

The vaginal and seminal microbiomes are deeply interconnected. If either is out of balance, it can increase the risk of BV, HPV persistence, and other reproductive issues.

By understanding these microbiomes and taking proactive steps to support microbial health, both partners can contribute to better sexual health, reduced BV recurrence, and improved fertility outcomes.

💜 Your microbiome matters. Your health is a shared journey. Let’s take care of it together!

👉 Interested in learning more about your vaginal or seminal microbiome? ScreenMe’s advanced testing and expert support can help you take charge of your reproductive health.

Jessica Hobbis