The bladder is not sterile, even when not suffering from urinary tract infections (UTIs). Instead, it's common for the bacteria from the female reproductive tract to also occur in the bladder, and some of them may even have a beneficial role. If this is the case, it may be that the use of antibiotics to treat UTIs is counterproductive, and we need to get smarter about how we tackle them.
Bacterial infections of the bladder and urinary tract inflict a heavy cost, causing 70,000 hospitalizations a year even in Australia's relatively small population. Until now, the only bladder bacteria that scientists could culture were those found during painful attacks, which made it easy to assume an absence of microbes at other times. And while taking antibiotics always carries a risk of resistance and can be damaging for the “good bacteria” in the body, at least it didn’t seem to do any harm for the target area.
Now, however, a study in Nature Communications has announced the identification of 149 bacterial species, dubbed a “mini-microbiome”, in the bladders of 77 women. Although a few of these are associated with painful UTIs, others are not. Moreover, many are the same bacteria whose presence is known to be beneficial in the female reproductive tract, raising the possibility they provide a similar service elsewhere.
Dr Samuel Forster of Australia's Hudson Institute told IFLScience it is too early to tell which bacteria, if any, are improving women's health with their presence in the bladder, but the work gives scientists the tools to investigate.
When harmless bacteria take hold in some parts of the body, they prevent damaging ones occupying the same space, a process known as colonization resistance. Taking antibiotics kills the protective bacteria, often making it easier for toxin-producing species to grab the vacated territory.
However, Forster cautioned: “We have difficulty defining what is good bacteria and what is bad. Most sit somewhere on a continuum.” The fact certain bacteria are useful in women's reproductive tracts does not mean the same is true in the bladder, although certain species appear to be associated with reduced UTI risk.
Nevertheless, Forster thinks: “The prospects of being beneficial are quite high,” since the immune system doesn't seem to be making any effort to rid us of these species.
The work so far has been restricted to the female urinary tract, with the researchers confirming that the same species were frequently present in individuals' reproductive and urinary tracts, suggesting migration between the two.
Forster said previous investigations missed the presence of these bacteria because we lacked the capacity to culture the relevant species. His co-authors have developed new culturing techniques that proved the bacteria found between infections are live, rather than dead cells passing through.