The Predictive Utility of Prior Positive Urine Cultures.
Clin Infect Dis. 2014 Jul 21;
Authors: MacFadden DR, Ridgway JP, Robicsek A, Elligsen M, Daneman N
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 a patient's previous urine cultures predict the identity and susceptibility of subsequent urine cultures.
METHODS: We conducted a multi-national, multi-centre, retrospective cohort study, including 22,019 pairs of positive urine cultures from 4,351 patients, across two 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, correspondence of isolate identity was 57%(95%CI: 55-59%), and at >32 weeks was 49%(95%CI:48-50%), still greater than expected by chance(p<0.001). At 4-8 weeks, a same or better susceptibility profile was found in 83%(95%CI:81-85%) of isolate pairs, and at >32 weeks 75%(95%CI:73-77%), still greater than expected by chance(p<0.001). Despite high local rates of ciprofloxacin resistance in urine isolates across all patients (40%,95%CI 39.5-40.5%), ciprofloxacin resistance was less than 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 no history of intervening fluoroquinolone use.
PMID: 25048850 [PubMed - as supplied by publisher]