Predictive utility of prior positive urine cultures

Clin Infect Dis. 2014 Nov 1;59(9):1265-71. doi: 10.1093/cid/ciu588. Epub 2014 Jul 21.


Background: A patient's prior urine cultures are often considered when choosing empiric antibiotic therapy for a suspected urinary tract infection. We sought to evaluate how well previous urine cultures predict the identity and susceptibility of organisms in a patient's subsequent urine cultures.

Methods: We conducted a multinational, multicenter, retrospective cohort study, including 22 019 pairs of positive urine cultures from 4351 patients across 2 healthcare systems in Toronto, Ontario, and Chicago, Illinois. We examined the probability of the same organism being identified from the same patient's positive urine culture as a function of time elapsed from the previous positive urine specimen; in cases where the same organism was identified we also examined the likelihood of the organism exhibiting the same or better antimicrobial susceptibility profile.

Results: At 4-8 weeks between cultures, the correspondence in isolate identity was 57% (95% confidence interval [CI], 55%-59%), and at >32 weeks it was 49% (95% CI, 48%-50%), still greater than expected by chance (P < .001). The susceptibility profile was the same or better in 83% (95% CI, 81%-85%) of isolate pairs at 4-8 weeks, and 75% (95% CI, 73%-77%) at >32 weeks, still greater than expected by chance (P < .001). Despite high local rates of ciprofloxacin resistance in urine isolates across all patients (40%; 95% CI, 39.5%-40.5%), ciprofloxacin resistance was <20% among patients with a prior ciprofloxacin sensitive organism and no subsequent fluoroquinolone exposure.

Conclusions: A patient's prior urine culture results are useful in predicting the identity and susceptibility of a current positive urine culture. In areas of high fluoroquinolone resistance, ciprofloxacin can be used empirically when prior urine culture results indicate a ciprofloxacin-susceptible organism and there has been no history of intervening fluoroquinolone use.

Keywords: antimicrobial resistance; nosocomial infection; stewardship.

Publication types

  • Multicenter Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Aged, 80 and over
  • Anti-Bacterial Agents / pharmacology*
  • Bacteria* / drug effects
  • Bacteria* / isolation & purification
  • Bacteriuria* / diagnosis
  • Bacteriuria* / epidemiology
  • Bacteriuria* / microbiology
  • Chicago / epidemiology
  • Ciprofloxacin / pharmacology
  • Cross Infection* / epidemiology
  • Cross Infection* / microbiology
  • Drug Resistance, Bacterial*
  • Female
  • Humans
  • Male
  • Microbial Sensitivity Tests
  • Middle Aged
  • Ontario / epidemiology
  • Retrospective Studies
  • Urinary Tract Infections / epidemiology
  • Urinary Tract Infections / microbiology


  • Anti-Bacterial Agents
  • Ciprofloxacin