• A unique microbiota
• Genetic factors
What is already known on this topic
Contrary to popular belief, the urinary tract is not sterile. Recent studies have shown that the urinary tract is home to its own microbiota, reflective of the microbes inhabiting the bladder and associated organs. However, scientists so far have mostly focused on the urinary microbiota in relation to urinary tract infections.What this research adds
Researchers analyzed urine samples from 1,600 healthy women who were on average 66 years old and had no apparent urinary tract infection. They found that the urinary microbiota is distinct from the gut microbiota, with more Actinobacteria, Fusobacteria, and Proteobacteria, but fewer Bacteroidetes, Firmicutes, and Verrumicrobia. Older age tended to associate with increased microbial diversity.Conclusion
The findings reveal the factors that influence the composition of the urinary microbiota in older women.
Contrary to popular belief, the urinary tract is not sterile. Now, researchers have identified the factors that influence the composition of the urinary microbiota in older women.
The study, published in Cell Host & Microbe, is the first to look at the microbes present in the urinary tracts of a large number of healthy adult women.
Several recent studies have shown that the urinary tract is home to its own microbiota, reflective of the microbes inhabiting the bladder and associated organs. However, scientists so far have mostly focused on the urinary microbiota in relation to urinary tract infections, and studies that looked at the urinary and bladder microbiotas have involved only dozens or few hundreds of people.
To characterize the host influence on the urinary microbiota of healthy people, Claire Steves at King’s College London and her colleagues analyzed urine samples from 1,600 women who were on average 66 years old and had no apparent urinary tract infection.
A unique microbiota
The researchers found that the urinary microbiota is distinct from the gut microbiota. For example, the urinary microbiota has higher levels of Actinobacteria, Fusobacteria, and Proteobacteria, but lower levels of Bacteroidetes, Firmicutes, and Verrumicrobia than the gut microbiota. This suggests that the urinary tract has its own unique microbiota, the researchers say.
However, the bacteria found in urine varied greatly from person to person. The researchers found that age, menopausal status, previous urinary tract infections, and genetics are the main factors that define the urinary microbiota. In particular, older age tended to associate with increased microbial diversity, whereas diet and antibiotics use had a smaller effect on the diversity of microbes present in the urinary tract.
Genetic factors
The team also found that bacteria belonging to the Escherichia-Shigella taxon—which are considered potential culprits in urinary tract infections—were part of the urinary tract microbiota in older women. In the absence of urinary tract infections, the presence of this taxon is influenced by the host genetic make-up and age. This result could explain the mixed success of E. coli vaccine trials in women with recurrent urinary tract infections, the researchers say.
Although the study reveals that age and genetics can influence the urinary microbiota in older women, more work is needed to confirm if the findings also relate to the male urinary microbiota. “Further research will need to focus on the differences between males and females and how this may affect susceptibility to infections,” says study first author Adewale Adebayo.
Acknowledging the study participants, Steves says that donating a urine sample may not be a glamorous task. “But it has allowed us to get the first real sense of what a healthy [urinary microbiota] looks like and what factors affect it,” she says. “This is invaluable for future studies of the [urinary microbiota].”
