Women with symptoms of a urinary tract infection but a negative urine culture: PCR-based quantification of Escherichia coli suggests infection in most cases

Clin Microbiol Infect. 2017 Sep;23(9):647-652. doi: 10.1016/j.cmi.2017.04.004. Epub 2017 Apr 28.


Objectives: Our objective was to examine whether or not women with symptoms of a urinary tract infection but with a negative culture (20%-30%) do have an infection.

Methods: We performed quantitative PCR (qPCR) for Escherichia coli and Staphylococcus saprophyticus, on top of a standard culture, in urine samples from 220 women with dysuria and/or frequency and/or urgency and from 86 women without symptoms. For symptomatic women, qPCR was also carried out for four sexually transmitted agents.

Results: In the symptomatic group, 80.9% (178/220) of the urine cultures were positive for any uropathogen and 95.9% (211/220) were E. coli qPCR-positive. For the control group, cultures for E. coli and E. coli qPCR were positive in, respectively, 10.5% (9/86) and 11.6% (10/86). In the symptomatic group, qPCR yielded 19 positive samples for S. saprophyticus qPCR, one positive sample for Mycoplasma genitalium and one for Trichomonas vaginalis.

Conclusions: These findings suggest that almost all women with typical urinary complaints and a negative culture still have an infection with E. coli.

Keywords: Escherichia coli; Primary care; Quantitative PCR; Standard urine culture; Urethral syndrome; Urinary symptoms; Urinary tract infections; Urinary tract infections in women.

MeSH terms

  • Adult
  • Bacteriological Techniques / methods*
  • Bacteriuria
  • Escherichia coli / genetics*
  • Escherichia coli / isolation & purification
  • Female
  • Humans
  • Middle Aged
  • Polymerase Chain Reaction / methods*
  • Staphylococcus saprophyticus / genetics
  • Staphylococcus saprophyticus / isolation & purification
  • Urinary Tract Infections* / diagnosis
  • Urinary Tract Infections* / epidemiology
  • Urinary Tract Infections* / microbiology
  • Young Adult