Is it a urinary tract infection?

Whilst the respiratory tract is the most frequent site of infection, in the developed world the urinary tract is the second most frequent site; 50% of otherwise healthy women will experience at least one UTI. The shortness of the female urethra and its proximity to both vagina and anus in women contribute to the much greater frequency of UTIs in women compared with men. Sexually active women are most vulnerable to infection, and up to 40% of women who have a UTI will experience a repeat infection within a year. Quite apart from the extreme discomfort that uncomplicated UTIs can cause, complications such as pyelonephritis can lead to pyonephrosis, sepsis and kidney failure. Thus, diagnosed UTIs are treated with antibiotics such as trimethoprim, alone or in combination with sulfamethoxazole.

However, resistance to antibiotics and the urgent need for ‘antibiotic stewardship’ is rightfully discouraging primary healthcare providers from prescribing these drugs without a diagnosis of a bacterial infection. This is especially relevant in the case of upper respiratory tract infections, which are most frequently viral and self-limiting. But in the case of UTIs the dipstick test, and even standard lab-cultured urine, can give false negative results resulting in the withholding of necessary treatment. A recently published Belgian study based at the University of Ghent carried out quantitative PCR on urine samples for two bacterial species (and four sexually transmitted pathogens), in addition to standard urine culture, in 220 women with symptoms of UTI and 86 healthy volunteers. The tested bacterial species were Escherichia coli, present in the intestinal flora and the causative organism of over two thirds of UTIs, and Staphylococcus saprophyticus, the second most common causative organism present in the normal perineal and vaginal flora. In the symptomatic group standard culture detected uropathogens in 81% of the urine samples, but with qPCR 95.9% of these samples were found positive for E.coli and 8.6% for S. saprophyticus. There were also two samples positive for sexually transmitted pathogens. Overall 98% of the symptomatic women were found to have pathogens in their urine, compared with 10% of the control women.

So standard urine culture is not as infallible as was previously thought and dipstick tests, whilst quick and cheap, cannot be used to rule out a UTI. Because of the reliance on such tests, many women presenting with a UTI are sent home again without antibiotics being prescribed. Yes, we need stewardship, but clearly women with the typical urinary symptoms have an infection that should be treated!