Discovery of bladder ‘mini-microbiome’ signals UTI treatment change

Cutting edge genomics has now shown the female bladder is home to a community of bacteria – similar to the gut microbiome – even in the absence of infection.

Dr Sam Forster

A team of microbiologists and genomics experts from the Wellcome Sanger Institute (Cambridge, UK), Loyola University Chicago (USA) and Hudson Institute of Medical Research (Melbourne, Australia) made the discovery.

The findings of the study have been published in the journal Nature Communications.

“The female bladder has long been considered sterile except in women with urinary tract infections,” Dr Samuel Forster, joint-first author and research group head at Hudson Institute of Medical Research, says.

“Now, medical genomics is superseding over 100 years of medical dogma by showing bacteria associated with health in the female reproductive tract are also able to colonise the bladder without causing clinical infection.”

In a first, the team isolated and genome-sequenced 149 strains of bacteria found in urine samples from 77 healthy and symptomatic pre-menopausal women, then grew them in the laboratory to create a ‘living library’ of bacteria outside of the human body.

Bad or good bacteria? Depends on the environment

Dr Forster says the research could provide new treatment approaches for urinary tract infections and urinary incontinence, which account for one to two per cent of all GP consultations.

More than 70,000 people are hospitalised with kidney and urinary tract infections in Australia each year, and antibiotics are the most common form of treatment.

“This research completely redefines the way we think about bacteria in the bladder and female reproductive tract. It has the potential to fundamentally change the way we treat urinary tract infections and diseases,” Dr Forster says.

“This knowledge also raises the question – if antibiotics are used to kill the ‘bad’ bacteria in patients with urinary tract infections, could this also upset the balance of healthy bacteria that have a protective effect – much like in the gut?

“More research is needed to examine whether bacteria associated with health or disease in the female reproductive tract have the same positive or negative effect in the bladder, and vice versa.”

Culture club

Before now, standard pathology tests have been used to detect some pathogens in the female bladder, including E.coli. Now, using genomics, the team has shown healthy and disease-causing bacteria could move freely between the bladder and female reproductive tract – even in healthy women.

Strains detected in the bladder of healthy women and those with infections include E.coli (Escherichia coli), which is associated with urinary tract infections (UTIs), the emerging uropathogen Streptococcus anginosus, and Lactobacillus crispatus, a form of ‘good’ bacteria found in the female reproductive tract.

“We’ve shown that about two-thirds of all bacterial species found in the bladder are also found in the female reproductive tract. This suggests the female bladder is not sterile, and is part of an interconnected bacterial community with the female reproductive tract,” Dr Forster says.

In 2016, Dr Forster was part of the team that cultured more than 130 bacteria from the human gut for the first time, with the findings published in the journal Nature.

“While the bacteria in this bladder ‘mini-microbiome’ are much lower in numbers and diversity than the gut microbiome, it still gives us important clues about health and disease.

Dr Samuel Forster was generously supported by the National Health and Medical Research Council (NHMRC) CJ Martin Biomedical Fellowship: 1091097

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