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JU INSIGHT Predicting Antibiotic Susceptibility Among Patients With Recurrent Urinary Tract Infection
By: Marissa A. Valentine-King, PhD, Baylor College of Medicine, Houston, Texas, Center for Innovations in Quality, Effectiveness and Safety (IQuESt), Michael E. DeBakey Veterans Affairs Medical Center, Houston, Texas; Barbara W. Trautner, MD, PhD, Center for Innovations in Quality, Effectiveness and Safety (IQuESt), Michael E. DeBakey Veterans Affairs Medical Center, Houston, Texas, Baylor College of Medicine, Houston, Texas; Roger J. Zoorob, MD, MPH, Baylor College of Medicine, Houston, Texas; Jason L. Salemi, PhD, College of Public Health, University of South Florida, Tampa; Kalpana Gupta, MD, MPH, Boston Veterans Affairs Healthcare System and Boston University School of Medicine, Massachusetts; Larissa Grigoryan, MD, PhD, Baylor College of Medicine, Houston, Texas, Center for Innovations in Quality, Effectiveness and Safety (IQuESt), Michael E. DeBakey Veterans Affairs Medical Center, Houston, Texas | Posted on: 19 Jan 2024
Valentine-King MA, Trautner BW, Zoorob RJ, Salemi JL, Gupta K, Grigoryan L. Predicting antibiotic susceptibility among patients with recurrent urinary tract infection using a prior culture. J Urol. 2024;211(1):144-152.
Study Need and Importance
Patients with recurrent cystitis have a greater risk of having a UTI caused by an antibiotic-resistant uropathogen, which creates a challenge for choosing the correct empiric therapy. Recurrent cystitis guidelines recommend relying on a local antibiogram or prior urine culture to guide empirical prescribing, yet little data exist to quantify the predictive value of a prior culture. We created a urinary-specific antibiogram and evaluated the utility of a prior urine culture for predicting subsequent antibiotic resistance and susceptibility among patients with uncomplicated, recurrent cystitis in primary care or urology clinics.
What We Found
We included 597 visits from 232 patients with recurrent cystitis, and half of visits lacked a urine culture. Our urinary Escherichia coli antibiogram (median isolate number: 100) revealed considerable antibiotic resistance to earlier generation cephalosporins (>52%), trimethoprim-sulfamethoxazole (SXT; 38%), and fluroquinolones (27%-28%), but preserved activity to nitrofurantoin (5.5% resistance). Prior cultures (within 2 years) had good predictive value for detecting future susceptibility to first-line agents nitrofurantoin (85% probability) and SXT (78% probability) and excellent predictive value (≥90% probability) for cefepime, ceftriaxone, cefuroxime, ciprofloxacin, levofloxacin, gentamicin, tobramycin, piperacillin-tazobactam, and imipenem (Table).
Table. Test Metric Results From Comparing Paired, Gram-Negative Organisms by Antibiotic
| Antibiotic (No. of isolates) |
Resistance, %a |
Median d (quartiles) between cultures |
Sensitivity (95% CI)b |
Bayes’ PPV (95% CI)c |
Specificity (95% CI)d |
Bayes’ NPV (95% CI)e |
|---|---|---|---|---|---|---|
| AMC (n = 58) | 25.4 | 99 (30-183) | 0.53 (0.28-0.77) | 0.48 (0.30-0.67) | 0.80 (0.65-0.91) | 0.83 (0.75-0.89) |
| Ampicillin (n = 56) | 61.4 | 99 (31-178) | 0.85 (0.71-0.94) | 0.84 (0.69-0.92) | 0.73 (0.45-0.92) | 0.76 (0.59-0.88) |
| Cefazolin (n = 31) | 48.4 | 100 (29-214) | 0.88 (0.62-0.98) | 0.67 (0.52-0.80) | 0.60 (0.32-0.84) | 0.84 (0.57-0.95) |
| Cefepime (n = 33) | 6.9 | 91 (31-150) | 0.33 (0.04-0.78) | 0.25 (0.05-0.66) | 0.93 (0.76-0.99) | 0.95 (0.91-0.97) |
| Ceftriaxone (n = 55) | 16.4 | 98 (26-177) | 0.92 (0.64-1.00) | 0.72 (0.46-0.88) | 0.93 (0.81-0.99) | 0.98 (0.90-1.00) |
| Cefuroxime (n = 42) | 18.2 | 110 (33-254) | 0.71 (0.29-0.96) | 0.58 (0.33-0.80) | 0.89 (0.73-0.97) | 0.93 (0.81-0.98) |
| Ciprofloxacin (n = 55) | 24.9 | 91 (26-172) | 0.93 (0.66-1.00) | 0.76 (0.55-0.89) | 0.90 (0.77-0.97) | 0.97 (0.85-1.00) |
| Gentamicin (n = 34) | 13.3 | 90 (33-145) | 0.78 (0.40-0.97) | 1.00 (0.59-1.00) | 1.00 (0.86-1.00) | 0.97 (0.90-0.99) |
| Levofloxacin (n = 57) | 24.4 | 98 (22-175) | 0.87 (0.60-0.98) | 0.70 (0.50-0.85) | 0.88 (0.74-0.96) | 0.95 (0.85-0.99) |
| Nitrofurantoin (n = 57) | 18.5 | 98 (29-175) | 0.36 (0.11-0.69) | 0.32 (0.15-0.56) | 0.83 (0.69-0.92) | 0.85 (0.78-0.90) |
| Tetracycline (n = 41) | 40.5 | 112 (37-258) | 0.71 (0.42-0.92) | 0.69 (0.50-0.83) | 0.78 (0.58-0.91) | 0.80 (0.63-0.90) |
| SXT (n = 54) | 32.2 | 95 (30-172) | 0.55 (0.32-0.77) | 0.53 (0.35-0.70) | 0.76 (0.59-0.89) | 0.78 (0.68-0.86) |
| Imipenem (n = 31) | 0.9 | 79 (34-115) | f | f | 0.97 (0.83-1.00) | 0.99 (0.99-0.99) |
| PCT (n = 29) | 4.8 | 88 (22-175) | f | f | 0.89 (0.71-0.98) | 0.95 (0.94-0.95) |
| Tobramycin (n = 32) | 10.5 | 84 (22-175) | 0.75 (0.35-0.97) | 1.00 (0.54-1.00) | 1.00 (0.86-1.00) | 0.97 (0.91-0.99) |
| Median No. (quartiles) of paired isolates (n = 42, 31-56) | 21.7 | 98 (30-175)g | 0.75 (0.40-0.96)g | 0.69 (0.50-0.83)g | 0.89 (0.73-0.97)g | 0.95 (0.85-0.97)g |
| Abbreviations: AMC, amoxicillin-clavulanic acid; NPV, negative predictive value; PCT, piperacillin-tazobactam; PPV, positive predictive value; SXT, sulfamethoxazole-trimethoprim. aResistance levels among all gram-negative organisms. bSensitivity: ability of a prior culture to detect all those with future resistance (see formulas in Figure 1). cPPV: probability of a prior resistant culture to accurately predict future resistance. dSpecificity: ability of a prior culture to detect all those with future susceptibility. eNPV: probability of a prior susceptible culture to accurately predict future susceptibility. fCalculation results not presented as zeros were present in one part of the sensitivity or PPV formula (eg, imipenem and PCT had zero true positives). gCalculated the median of the median number of days between cultures for each antibiotic and the median of the first and third quartiles for each antibiotic. |
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Limitations
Our study included patients from 3 clinics in a single academic medical center. The study was retrospective and relied on electronic medical records. As we excluded patients with complicated UTI and had a low number of men in our study, our findings are not necessarily applicable to these populations.
Interpretation for Patient Care
Antibiotic resistance among E coli exceeded 20% to several antimicrobials. Providers should consider referring to a prior urine culture for guidance when treating cystitis, as susceptibility on the prior culture had good predictability of future susceptibility for SXT and nitrofurantoin, and excellent predictability for aminoglycosides, cefepime, ceftriaxone, cefuroxime, and fluoroquinolones.
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