Microbiota is the collective term for all of the microbes (bacteria, viruses and fungi) in a specific area of the body. It is often called the microbiome (although this technically refers to the genetic information of the microbiota). Your urovaginal tract (including the vulva, vagina, urethra and bladder) has its own unique microbiota, as does each individual area, e.g., the vulva and vagina have different microbiota, but they influence each other, often sharing microbes. Various problems and infections can occur if these become unbalanced (1).
How does your urovaginal microbiota become unbalanced?
In most areas, it is best to have a diverse microbiota made up of a wide variety of microbes. In the urovaginal tract, however, it is generally best to have mostly lactobacilli (2). Lactobacilli thrive in the vagina where they use vaginal mucins as a food source. These lactobacilli fill the niche of the vagina, forming a layer that physically prevents other microbes from accessing vaginal cells and growing into an active infection. Lactobacilli also produce lactic acid. This is why the optimal vaginal pH is quite acidic, around pH 4 - 4.5. This acid acts as a chemical barrier against pathogens. The diagram below shows how bacteria from the gut can travel from the rectum to the vagina. This is very rarely a result of poor hygiene, but rather an unfortunate effect of anatomy. Women generally have a short urethra and a very short distance between the anus and vagina, with no external genitalia (like testicles) forming a physical barrier against pathogens.
Infectious microbes often come from our own bodies. Yeasts and bacteria that usually live in small quantities in our vaginas, causing no problems, can overgrow in certain conditions. Too much Candida (a very common yeast) can cause Thrush. Bacteria that live on the vulva (external genitalia) can invade the vagina and cause Aerobic Vaginitis (AV) or Bacterial Vaginosis (BV).
Pathogens can also come from external sources, even a male sexual partner (3). Everyone is familiar with the fact that microbes can transfer from person to person during sex in the form of STIs, such as gonorrhea, chlamydia and HIV. But it may come as a surprise that other microbes that can live on the penis can also be transferred to female partners, causing infections like UTI (Urinary Tract Infection), BV/AV, and HPV (Human Papillomavirus, an incredibly common virus that is screened for during a pap smear and can cause cervical cancer if left unchecked). Unfortunately, a major risk factor for UTI is the use of spermicides, which are still on many condoms and commonly used with diaphragms.
Why does Lactobacillus not protect against infections?
Unfortunately, many things can disrupt the balance of lactobacilli in the vagina. Stress and illness can put the immune system under pressure so that our natural defenses can’t fight invading pathogens. Exercise or wearing tight clothes and underwear can create a warm, humid environment in the genital area. These are ideal conditions for pathogens to thrive. Hormonal changes can alter vaginal cells and make them less hospitable to lactobacilli (4). This is common leading up to a period (menstruation) and during pregnancy, but is most pronounced during menopause. Perimenopause, the time when periods are few and erratic before they stop completely post menopause, is caused by a drop in estrogen levels. Reduced estrogen causes the vaginal wall to become thin and dry (stops producing mucous). Without mucins to feed on, lactobacilli decline and leave the area open to colonisation by other microbes. UTIs are particularly common during menopause, when bacteria like E. coli invade the urethra and can spread to the bladder and even kidneys.
In an unfortunate twist of events, often the treatment of one infection can lead to further infections. Broad-spectrum antibiotics are medicines that kill a wide range of bacteria. These are prescribed for a host of infections all over the body. While they may target the bacterium that is causing the infection, they often also kill healthy and protective microbiota, such as lactobacilli in the vagina. It is very common to get Thrush, UTIs or BV following a course of antibiotics.
What can be done to protect my healthy microbiota?
A healthy diet is always a good place to start for a healthy microbiota. High fibre, low sugar diets are good for the gut and, in turn, good for the whole body. Some people report that they are more prone to infections following alcohol or caffeine consumption. Our bodies are complex, and it is not possible to determine the perfect diet for everyone. It is also likely a combination of multiple factors that induce these infections, and impossible to narrow it down to one causative agent. There are many probiotics on the market containing lactobacilli and other “good” bacteria. It is possible that these could reach the gut and, eventually, the urovaginal tract. There are also vaginal suppositories that are directly inserted into the target area. These may help establish new populations of protective lactobacilli (5), but the species included in commercial products can vary greatly, and they are not always the same kinds that colonise us naturally.
Citations:
1. Banerjee S, Robertson E S, Future perspectives: microbiome, cancer and therapeutic promise, Microbiome and Cancer p363-389, 2019
2. Ravel J, Gajer P, Abdo Z, Forney L J, Vaginal microbiome of reproductive-age women, Proc Nat Acad Sci USA 108:4680-87, 2010
3. Onywera H, Williamson A, Ponomarenko J, Meiring T L, The penile microbiota in uncircumcised and circumcised men: relationships with HIV and Human Papillomavirus infections and cervicovaginal microbiota, Front Med 7:383, 2020
4. Amabebe E, Anumba D O C, The vaginal microenvironment: the physiologic role of lactobacilli, Front Med 5:181, 2018
5. Cribby S, Taylor M, Reid G, Vaginal microbiota and the use of probiotics, Interdiscip Perspect Infect Dis 256490, 2008
