Contrary to popular belief, urine is not sterile and contains a range of microbiological organisms that vary in health and disease, US scientists have shown.
According to research presented at the American Society for Microbiology 114th General Meeting, held in Boston, Massachusetts, the urinary microbiota is more diverse in women with lower urinary tract symptoms than in healthy individuals, a difference with potential clinical implications.
“If we determine that certain bacteria cause OAB [overactive bladder] symptoms, we may be able to better identify those at risk for this condition and prevent or more effectively treat affected patients,” said Evann Hilt (Loyola University, Chicago, Illinois, USA), the lead investigator, in a press statement.
Received wisdom among physicians is that urine is sterile. However, in 2012, Hilt’s team used expanded quantitative urine culture (EQUC) – a new DNA-based detection method – to show that urine contained bacteria that could not be found by standard techniques.
In the latest study, the team used EQUC and standard methods to characterise the microbiota in urine samples from 42 women with OAB and 42 women without urinary symptoms. Matrix-assisted laser desorption–ionisation time-of-flight mass spectrometry was used to classify bacterial isolates.
Bacteria were detected in just 10% of samples by standard techniques compared with 71.4% of samples using EQUC, the authors report.
Interestingly, the microbiota was more diverse in OAB patients than in controls; a total of 217 bacteria from 77 genera were isolated from women with OAB versus 66 bacteria from 33 genera from controls.
Organisms that were present only in urine from OAB patients included Actinobaculum schaalii, Aerococcus urinae, Arthrobacter cumminsii and Oligella urethralis, all of which have been implicated in the aetiology of urinary tract infections, note Hilt et al.
The team believes that bladder bacteria may be partially responsible for the failure of treatment in approximately 40% to 50% of women with OAB. “Further research is needed to determine if these bacterial differences are clinically relevant for the millions of women with OAB and the doctors who treat them”, they conclude.
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