What bacteria live in the vagina?

I’m going to focus on the bacteria in the vagina.  The opening to the bladder, or the urethra, sits right by the vagina and the bacteria in the vagina can impact the bladder.  There is ongoing research looking at the small amounts of bacteria in the bladder but this is fairly preliminary.

There are different bacteria that live in the vagina and they change based on race, hormonal status, sexual activity, age, and even where you live.  Lactobacilli are the “good “ bacteria that are commonly found in the vagina.  They do many things including release lactic acid, maintain an acidic environment, and modulate the local host immune system (the vagina’s ability to fight infection).  There are different types of lactobacilli.  Lactobacillus crispatus (L. crispatus), L. iners, L. gassen, and L. jensenii are found in most women.  A fifth lactobacillus can also be found (usually L. reuteri, L. rhamnosus, L. vaginalis, or L. gallinorum) and this type depends on where you live.  L. Crispatus and L. iners are the most common lactobacilli in the vagina.

Which type of lactobacillus helps against urinary tract infections?

While you might think that probiotics should contain the more common types of lactobacillus, that isn’t true.  Each type of lactobacillus does different things.  L. rhamnosus (also called LGR-1 in research studies) is the most studied type of lactobacillus and may help with recurrent urinary tract infections.  This bacteria can help prevent biofilms- something “bad” bacteria create that makes it harder to treat the infection.  L rhamnosus can also help break down biofilms and is naturally resistant to many antibiotics (which means you could take an antibiotic to treat the infection and a probiotic at the same time).  When taken as a pill, the lactobacilli get to the vagina (which is what you want).  When put in the vagina, the lactobacilli stay in the vagina for about 3 weeks (but it isn’t clear how long the impact will last).  But most of this data is from a lab and not from human studies which leaves lots of questions.  While the existing data looks promising, we need more data to know:

1. how it works
2. who it works for
3. how long it works
4. the best way to take the probiotic (by mouth or inserting it in the vagina)

There is also some ongoing work looking at L. crispatus for recurrent urinary tract infections.  There haven’t been as many studies on this type of lactobacilli but there is a human trial which will hopefully produce positive results.

What type of probiotic should I buy?

When you look at actual probiotics, they commonly contain L. rhamnosus along with many other types of bacteria.  But we don’t really know how well these “mixes” work.  I couldn’t find any studies looking at brands of probiotics and their impact on recurrent bladder infections.  Since each bacteria works differently on the cells, we don’t know how the different combinations of bacteria work together.  And while probiotic companies make a lot of claims, there is usually limited data.  If you like the idea of a probiotic to help with UTI’s, make sure it contains L. rhamnosus.  There is no way to say which brand works the best.  And keep an eye out for new data.  These is a really promising area of research and it is continually evolving.

Looking for more information about probiotics and bladder infections?  Check out this article in Today’s Dietician or this article from Harvard Health Publishing.

Why won’t I recommend something if it sounds like a good thing?

There have been lots of things over time that sounded like a good idea but turned out to be unhelpful or even harmful.  Data from a lab setting tells us what looks promising but it doesn’t tell us how it will work in humans.  Fore example, lactobacilli kill yeast in the lab but not in the vagina.  It isn’t until we have really good research studies that we know how well something will work.  I tend to always be a little skeptical until I have the right data in hand.  In general, probiotics are a good idea.  They won’t hurt you.  But they are expensive and they may not be doing everything that you hope for.

Saraf VS et al. Vaginal microbiome:normalcy vs dysbiosis. Arch Microbiol 2021;203:1793-802.

Neugent ML et al. Advances in understanding the human urinary microbiome and its potential role in urinary tract infection. mBIO 2020;11(2):e00218-20.

Stapleton AE et al. Randomized, placebo-controlled phase 2 trial of a lactobacillus crispatus probiotic given intravaginally for prevention of recurrent UTI. Clin Infect Dis. 2011;52(10):1212-17.