A frequent and sometimes uncontrollable urge to urinate, and a painful burning sensation when urinating: A bladder infection is extremely unpleasant for those affected - and for millions of women, it is a painful recurring routine in their lives. For them, cystitis is not a one-off event. Rather, it recurs every few weeks or months, with the same symptoms, pain and discomfort, which in many cases is followed by a visit to the doctor and a course of antibiotics.

And even if doctors, friends and the internet give a lot of well-intentioned advice, such as bladder teas, they can only really prevent recurrence in the rarest of cases. But now German scientists have discovered a completely new approach that could give new hope to the millions of women affected. In this article, we take a closer look at it and explain what needs to be considered and what this ground-breaking idea could mean for them.

Bladder inflammation, also known as cystitis, is an infection of the bladder that is usually caused by bacteria. These bacteria, mostly Escherichia coli (80%), but also Klebsiella or Pseudomonas aeruginosa, almost always enter the urethra from the outside through the vaginal opening and from there migrate upwards into the bladder.

There they trigger an inflammation, which then leads to the frequent, uncontrollable urge to urinate and a painful burning sensation.

The fact that women in particular are often affected by cystitis is due to the difference in physique between women and men: the path between the urinary outlet and the bladder is only 4 cm long in women, whereas it is 20 cm long in men, so that the harmful bacteria have to travel a much shorter distance into the bladder, where they can then cause damage.

But why are millions of women repeatedly affected by cystitis, while others never suffer from it? To understand this, it is first necessary to shed light on how the body actually protects itself against the possible triggers of cystitis, the harmful bacteria Escherichia coli, Klebsiellen or Pseudomonas aeruginosa.

The latest research findings show: The secret lies in the so-called vaginal microbiome, i.e. the natural community of beneficial bacteria found in a healthy vagina. What many people don't realise: Even though the term microbiome is often associated with the bacterial landscape in the gut, there are also beneficial bacteria in many other places in our body that play a crucial role in our well-being.

Examples include the skin, mucous membranes and the intimate area.

The healthy vaginal microbiome, like that of the intestine, consists of different bacterial strains. These bacteria have been a particular focus of research in recent years. Using state-of-the-art methods such as 16S rRNA-based gene sequencing, researchers have analysed the vaginal microbiomes of thousands of women.

They discovered that every vaginal microbiome is just as unique as a fingerprint - and just as diverse. While some bacterial species are found in the vaginal microbiome of the vast majority of women, others are found in less than one per cent of the samples examined.

When the researchers finally investigated the connection between the vaginal microbiome and recurrent bladder infections, they came to groundbreaking results: In studies on several continents, scientists were able to clearly show that these beneficial bacteria play a decisive role in preventing bladder infections by preventing the invasion of harmful germs, such as Escherichia coli, or by sustainably inhibiting their growth.

For example, Takanori Sekito and Koichiro Wada from Okayama University in Japan compared the vaginal microbiome of a group of healthy women with that of a group of women with recurrent cystitis.

The result: the vaginal microbiome of women with recurrent cystitis differs significantly from that of other women. In women who have not been plagued by cystitis for a long time, bacterial strains from the lactobacillus genus (i.e. lactic acid bacteria) dominate the vaginal microbiome - they often make up over 90 percent of the microbiome. Interestingly, it is by no means always the same lactobacillus strain that dominates.

Rather, it is different strains, for example of the Lactobacillus crispatus family (6 different strains) or Lactobacillus gasseri (3 different strains) - but always lactobacilli. In contrast, women with recurrent cystitis contained significantly fewer lactobacilli or they were even completely absent! Instead, their microbiome contained a high number of Enterobacteriaceae, which are associated with various symptoms. And, almost even more serious: even in women who previously did not have cystitis, a change in the bacterial landscape in favour of Enterobacteriaceae was often followed by the first occurrence of cystitis.

The scientific community was electrified: The vaginal microbiome apparently plays a crucial role in preventing recurrent cystitis. However, in order to develop effective new approaches, it was first necessary to understand how exactly the beneficial lactobacilli counteract the invasion of harmful bacteria such as Escherichia coli. Researchers on all continents eagerly set to work to shed more light on this connection. In recent years, this has resulted in a large number of studies that prove that various specific lactobacilli strains suppress harmful bacteria through several mechanisms.

A team led by Patricia L. Hudson from Massachusetts General Hospital and Caroline Mitchel from Harvard University have reached an important milestone in research into HOW the vaginal microbiome can prevent the development of recurrent cystitis. The authors found that lactobacilli that produce a lot of lactic acid as part of their glycogen metabolism in particular reduce the risk of bladder infections.

This is because they use lactic acid to create an acidic environment in the vagina, which corresponds to healthy vaginal flora.

In such an acidic environment, the growth of harmful bacteria such as Escherichia coli is significantly inhibited. The clear finding that underpins this mechanism of action: the lactobacilli strains that created a particularly acidic environment were also the most effective at inhibiting or even preventing the growth of harmful bacteria - the Lactobacillus gasseri family is particularly successful at creating such an acidic environment.

This proved that maintaining an acidic and therefore healthy environment in the vagina can make a decisive contribution to preventing recurring bladder infections.

Another mechanism by which some strains of lactobacilli counteract cystitis has become known, thanks in part to the work of the Gupta/Stapleton research group at Washington University in Seattle. Gupta and Stapleton showed that the beneficial bacteria produce hydrogen peroxide, which also inhibits or stops the growth of many pathogenic bacteria as Escherichia coli. The reason for hydrogen peroxide production lies in the type of beneficial bacteria: This is because lactobacilli are so-called anaerobic bacteria, i.e. they do not need oxygen to live; on the contrary, it can even be harmful to them.

They therefore "detoxify" oxygen via enzymes and use it to form hydrogen peroxide (chemically H₂O₂). As hydrogen peroxide inhibits the growth of harmful bacteria, the lactobacilli use this completely natural process to create a further mechanism that protects against bladder infections. Incidentally, the production of hydrogen peroxide is particularly pronounced in strains of the Lactobacillus crispatus family, as a separate study by Pirje Hütt and Eleni Lapp from the University of Tartu (Estonia) was able to show.

A final point emphasised by researchers from the Institute of Microecology in Germany, among others, is that lactobacilli can also form a dense bacterial lawn on the vaginal epithelial cells if they dominate the vaginal microbiome to a sufficient degree. The number of lactobacilli can reach up to 10 billion bacteria per millilitre of vaginal secretion. In this way, they take away the habitat of harmful bacteria such as Escherichia coli so that they cannot colonise. In this way, the beneficial lactobacilli can also prevent colonisation with harmful germs.

As bladder infections are often very unpleasant and painful, doctors are often forced to prescribe antibiotics. In the short term, these are also very effective because - despite increasing resistance - they usually succeed in killing the trigger, i.e. the harmful bacteria in the bladder. The problem with this is that antibiotics not only kill the harmful bacteria such Escherichia coli, but also the good bacteria such as the lactobacilli in the vaginal flora.

The result: a clear-cutting of the bacterial landscape, which significantly weakens the resistance of the vaginal microbiome to newly invading germs and makes it easier for them to colonise and cause a new infection.

And almost worse: as a team led by John R. Brannon from the University of Nashville/Tennessee in the USA discovered, it is not only newly invading germs that find it easier to colonise. In fact, the harmful bacteria Escherichia coli have developed a particularly unpleasant characteristic: they penetrate the cells of the vaginal epithelium and can survive antibiotic therapy.

When the antibiotics are then discontinued, these dangerous bacteria encounter a destroyed vaginal flora and can multiply almost unhindered - the basis for a renewed flare-up of cystitis.

So if antibiotics, probably the most important therapeutic approach for cystitis, can actually increase the risk of recurrence, many researchers have asked themselves how the knowledge gained in recent years on the importance of the microbiome in recurrent cystitis can be utilised.

On this basis, a research team from the German company SYNformulas aimed to find a long-term solution for the aforementioned recurring infections. Three important hypotheses for a corresponding preparation have emerged: