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Understanding Bacterial Vaginosis and Vulvovaginal Candida

WHAT Is Bacterial Vaginosis (BV)?

(edited by Sharon Erdrich)

Bacterial vaginosis (BV) is a common infection caused by an imbalance of bacteria in the vagina. Normally, the vagina has a balance of good and bad bacteria. However, when this balance is disrupted, it can lead to bacterial vaginosis.

What are the symptoms of BV?

BV commonly causes: 
  • A discharge that is thin greyish-white in colour, possibly blood stained (more common after sexual intercourse).
  • A strong fishy odour.
  • A vaginal pH above 4.5.
  • There may also be no signs or symptoms

What Causes BV?

BV can is a type of dysbiosis (an imbalance in the vaginal microbiota), creating a loss in beneficial Lactobacilli species, with increased hydrogen peroxide production. This results in changes to the vaginal pH, with increased growth of detrimental microbes, such as Gardnerella vaginalis and Prevotella bivia.

The risk of BV is increased with multiple sex partners, vaginal douching (cleansing the vagina with a liquid solution), smoking, usage of intra-uterine devices (IUD), using soaps that are scented, or a history of vaginal infections. Contracting BV increases the risk of  chlamydia and gonococcal infection, HIV, pre-term birth and deceased birth weight.

Beneficial species found in the vagina, such as L. crispatus and L. jensenii produce hydrogen peroxide and lactic acid, which can decrease the risk of BV. Detrimental species such as G. vaginalis can also produce a protective biofilm, helping their survival in the presence of hydrogen peroxide, lactic acid and protecting against the effects of antibiotics. L. reuteri and L. iners are common bacteria, which can disrupt this biofilm. Infection of G. vaginalis increases inflammation in the female genital tract, whilst further increasing detrimental bacterial species, which produce harmful toxins called lipopolysaccharides (LPS).

What is Vulvovaginal Candida (VVC)?

Vulvovaginal candida, commonly referred to as thrush, is caused by a yeast or fungal infection, affects the vagina and the vulva (the external genital area of a woman). It is caused by an overgrowth of a type of yeast called Candida, most commonly Candida albicans.

What Causes Candida?

Candida overgrowth can occur due to various factors such as antibiotic treatment, hormonal changes, a weakened immune system, high blood sugars or uncontrolled diabetes.  Having diabetes, pregnancy, hormone therapy and immunosuppression therapy can increase the risk of thrush developing.

Women taking oestrogen-containing oral contraceptives (the Pill) are at increased risk of thrush, as oestrogen plays a role in its virulence, interferring with the normal immune response to detrimental bacteria.

At least 75% of women are likely to have at least one occurrence of VVC in their lifetime.

A reduction in beneficial Lactobacillus species can cause an altered vaginal pH, reduction in hydrogen peroxide and increase in C. albicans.


Can Candida Be Transmitted Sexually?

Yeast infection is not typically considered a sexually transmitted infection (STI). Candida is naturally present in the vagina and doesn’t require sexual transmission to become overgrown. However, it is possible that sexual activity can contribute to the development or exacerbation of a yeast infection.

Factors such as changes in the pH, friction, or introduction of bacteria from sexual partners may increase the risk of developing a yeast infection. Additionally, individuals with multiple sexual partners may have a higher likelihood of experiencing recurrent yeast infections.

While sexual transmission is not the primary cause of vulvovaginal candida, it’s still essential for partners to communicate about any infections or symptoms to prevent potential transmission or re-infection. 

What is the vaginal-gut axis?

The gut-vaginal axis refers to the connection or communication pathway between the gastrointestinal (GI) tract, particularly the gut microbiome, and the vagina. Both the gut and the vagina host complex ecosystems of microorganisms, including bacteria, fungi, and viruses, which play crucial roles in maintaining health and regulating various bodily functions.

The gut microbiome consists of trillions of microorganisms that inhabit the digestive tract and contribute to multiple processes that benefit the host, including digestion, metabolism, and immune function. Similarly, the vaginal microbiome comprises a diverse array of microorganisms that inhabit the vaginal environment and help maintain vaginal health and homeostasis.

A link has been found between the rectal and vaginal microbiota.

Female infections. Candida, thrush bacterial vaginosis, bv

This is due to the close proximity of the rectum, providing pool of bacteria near the vagina, allowing for recolonisation of Lactobacillus after a disturbance in the microbial balance, following sex or douching. This close proximity also makes it easy for yeasts or fungus, such as Candida, to migrate from the rectum to the vagina.

Research suggests that there is a bidirectional relationship between the gut and vaginal microbiomes, which is mediated by various factors such as immune system function, hormonal fluctuations, and microbial metabolites. For example:

  • imbalances or disruptions in the gut microbiome can potentially influence the composition and health of the vaginal microbiome, and vice versa.
  • immune antibodies from sites in the mucous layer assisting with regulation of the microbial population, thus acting as a defense mechanism.
  • in the gut, antibodies assists with adhesion of bacteria to the mucous layer and to form a layer of protective biofilm.
  • beneficial Lactobacilli can be coated with immune antibodies, assisting their survival in the vagina.

How Does the Vaginal Microbiota Develop?

Several factors contribute to the development and composition of the vaginal microbiota:

  • Childbirth: The initial colonisation of the vaginal microbiota primarily occurs during childbirth, as the baby passes through the birth canal. During this process, the baby comes into contact with microorganisms present in the maternal vagina, which can influence the composition of the newborn’s microbiota. Thus, vaginal delivery is not only a source of gut microbiota but aids in early vaginal colonisation as well. Children born via C-section tend to have reduced gut microbial diversity.
  • Breastfeeding: Breast milk contains beneficial bacteria and unique components that can help support the development of a healthy microbiota in the infant, including in the gastrointestinal tract and potentially in the vaginal microbiota.
  • Environmental Exposures: Over time, environmental exposures, diet, hormonal changes, sexual activity, hygiene practices, and antibiotic use can also shape the composition and diversity of the vaginal microbiota.
  • Life Cycle Changes: When a women begins menstruating, oestrogen levels increase, resulting in increased levels of glycogen and thus the growth of Lactobacillus species, important for vaginal health. 

While initial colonisation of the vaginal microbiota occurs during childbirth, the composition can fluctuate throughout life in response to various factors. The maintenance of a healthy vaginal microbiota is important for preventing infections such as Candida and BV, and maintaining overall vaginal health.

What is the Role of The Vaginal Microbiota?

Lactobacillus are the predominant bacterial species in the healthy vaginal microbiota of most women. These bacteria are beneficial and play a crucial role in maintaining vaginal health by:

  • Producing hydrogen peroxide and lactic acid which helps maintain an acidic environment (optimal vaginal pH of between 3.8 to 4.2)
  • Producing antibacterial proteins called bacteriocin 
  • Inhibiting other species from sticking to the vaginal lining
  • Producing a protective biofilm around beneficial bacteria, inhibiting bacteria growth.

What is the Role Of Oestrogen in Candida Infections?

Oestrogen plays an important role in the vaginal environment and can influence the occurrence and severity of both candida (yeast) infections and bacterial vaginosis (BV) in several ways:

  1. Vaginal pH: Oestrogen helps maintain the acidic pH of the vagina, which is typically between 3.8 and 4.5. This acidic environment inhibits the overgrowth of harmful bacteria and fungi, including Candida. When oestrogen levels decrease, such as during menopause or certain phases of the menstrual cycle, the vagina may become less acidic, creating conditions that are more conducive to the growth of Candida and the bacteria associated with BV.
  2. Vaginal Microbiome: Oestrogen influences the composition of the vaginal microbiota, which naturally includes various bacteria and fungi. Lower levels of oestrogen can lead to changes in the balance of these microorganisms, potentially favouring the growth of Candida or the bacteria associated with BV.
  3. Vaginal Secretions: Oestrogen stimulates the production of glycogen in the cells lining the vagina. Glycogen serves as a substrate for the growth of Lactobacilli, which have an important role in vaginal health by producing lactic acid and hydrogen peroxide, contributing to the acidic environment and inhibiting the growth of problematic species.
  4. Vaginal Epithelial Integrity: Oestrogen helps maintain the integrity of the the lining of the vagina (called the vaginal epithelium). A healthy vaginal lining acts as a protective barrier against pathogens, including Candida and BV-associated bacteria. Lower oestrogen levels may compromise this barrier function, increasing susceptibility to infections.

In summary, oestrogen plays a crucial role in maintaining the balance of the vaginal environment, including the prevention of Candida overgrowth and BV. Changes in estrogen levels, such as those occurring during menopause, pregnancy, or the menstrual cycle, can affect vaginal pH, microbiota composition, vaginal secretions, and epithelial integrity, potentially influencing the occurrence and severity of Candida and BV.

How to Manage Vaginal Dysbiosis

Factors such as diet, nutritional and herbal interventions hygiene practices, sexual behavior, and medical interventions can all influence the balance of microorganisms in the vaginal microbiota. Additionally, interventions targeting gut health, such as probiotics or dietary changes, may indirectly impact vaginal health through the gut-vaginal axis. Here are some specific things that help manage, and prevent imbalances that can lead to Candida and BV.

  • Diet: What you eat plays an important role in the gut microbiota, faecal microbiota excretion and the immune system. A decrease in micronutrients, including vitamins A, C, D, E and beta-carotene, calcium and folate increase the chances of contracting BV. Regularly consuming a diet high in energy dense and high glycaemic foods can result in impaired immune function, increased oxidative stress, whilst increasing the chances of detrimental bacterial colonisation in the gut. High fat intake, including saturated and monounsaturated fats can double the risk of contracting BV, while a high carbohydrate and high calorie intake may increase Candida susceptibility.
  • Herbs: Use of herbal medicines can assist with BV, through their antimicrobial action and support to acidify the vagina. Herbal antifungals can be used to assist with the management of Candida.
  • Probiotics: Various strains of probiotics, taken orally, aid colonisation of the vagina. Others can reduce LPS-induced activation in the vagina and colon, minimising dysbiosis and inflammation. Various Lactobacillus species can increase dominance of beneficial Lactobacillus in the vagina, preventing BV and thrush. Probiotics can also be in products designed for vaginal insertion.
  • Self-care: Avoid using soap to clean the vulva (use only on the surrounding skin). Douche with water using hand-held shower head.
  • Clothing: Wear cotton or bamboo underwear and avoid nylon leggings and tights, including pantyhose.
  • Sexual Activity: having a single sexual partner reduces the risk of any vaginal infection. Using condoms can reduce the risk of many infections, including BV, as well as protecting against unwanted pregnancy.

BV and thrush may be caused by overgrowth in detrimental bacteria, which may increase the risk of health issues. A healthy microbiome, both in the gut and the vagina, plays an important role in reducing the risk of both conditions. If you suffer with any of the symptoms of these conditions, please contact a health professional for advice.

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