| Author | Affiliation |
|---|---|
| Michael Mohseni, MD | Mayo Clinic, Department of Emergency Medicine, Jacksonville, Florida |
| Emily C. Craver, MS | Mayo Clinic, Division of Clinical Trials and Biostatistics, Jacksonville, Florida |
| Michael G. Heckman, MS | Mayo Clinic, Division of Clinical Trials and Biostatistics, Jacksonville, Florida |
| Johnathan M. Sheele, MD, MPH, MHS | Mayo Clinic, Department of Emergency Medicine, Jacksonville, Florida |
ABSTRACT
Introduction
Urinary tract infections (UTI) are one of the most common infections encountered in the emergency department (ED) with an estimated 2–3 million annual visits. Commonly prescribed antibiotics for UTIs have shown growing rates of resistance. Previous studies lack direction on improving UTI treatment based on the labs available to the bedside clinician.
Methods
We sought to determine if antibiotic resistance in UTIs was related to demographics, urinalysis, and history of renal failure or kidney stones. We conducted an analysis of 892 women ≥18 years of age discharged from the ED with a UTI diagnosis. We assessed predictors of nitrofurantoin resistance, cefazolin resistance, ciprofloxacin resistance, and trimethoprim-sulfamethoxazole resistance using unadjusted and multivariable logistic regression models.
Results
Antibiotic resistance was 13.6% for nitrofurantoin, 11.9% for cefazolin, 12.8% for ciprofloxacin, and 17.1% for trimethoprim-sulfamethoxazole. In multivariable analysis, significant independent associations with an increased likelihood of resistance to nitrofurantoin were observed for less urine blood (OR [per 1 category increase of score] 0.81; P = 0.02); greater mucous (OR [per 1 category increase of score] 1.22; P = 0.02); less specific gravity urine (OR [per 1 category increase] 0.87; P = 0.04), and presence of any history of kidney stones (OR 3.24; P = 0.01). There were no significant predictors for cefazolin resistance (all P ≥0.06); age was the only significant predictor of ciprofloxacin resistance (OR per 10 year increase] 1.10, P = 0.05), and lower specific gravity urine was significantly associated with an increased risk of resistance to trimethoprim- sulfamethoxazole (OR [per 1 category increase] 0.88, P = 0.04).
Conclusion
Women with any history of kidney stones may have bacteriuria resistant to nitrofurantoin, suggesting that providers might consider alternative antibiotic therapies in this scenario.
Footnotes
Section Editor: Elissa Perkins, MD, MPH
Full text available through open access at http://escholarship.org/uc/uciem_westjem
Address for Correspondence: Michael Mohseni, MD, Department of Emergency Medicine, Mayo Clinic, 4500 San Pablo Rd, Jacksonville, FL 32224. Email: Mohseni.Michael@Mayo.edu. 9 / 2022; 23:613 – 617
Submission history: Revision received September 25, 2022; Submitted April 14, 2022; Accepted April 27, 2022
Conflicts of Interest: By the WestJEM article submission agreement, all authors are required to disclose all affiliations, funding sources and financial or management relationships that could be perceived as potential sources of bias. No author has professional or financial relationships with any companies that are relevant to this study. There are no conflicts of interest or sources of funding to declare.
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| Variable | N | Median (minimum, maximum) or No. (%) of patients |
|---|---|---|
| Age (years) | 892 | 49 (18, 103) |
| Race | 889 | |
| White | 474 (53.3%) | |
| Black | 405 (45.6%) | |
| Other | 10 (1.1%) | |
| Marital status | 890 | |
| Single | 423 (47.5%) | |
| Married | 259 (29.1%) | |
| Other | 208 (23.4%) | |
| Primary care doctor | 892 | 378 (42.4%) |
| Emergency severity index | 869 | |
| 1 | 1 (0.1%) | |
| 2 | 34 (3.9%) | |
| 3 | 568 (65.4%) | |
| 4 | 262 (30.1%) | |
| 5 | 4 (0.5%) | |
| Urine specimen source | 698 | |
| Clean catheter/voided urine | 631 (90.4%) | |
| Straight catheter or urine from new bladder catheter | 41 (5.9%) | |
| Bladder catheter not known to be new | 25 (3.6%) | |
| Suprapubic catheter | 1 (0.1%) | |
| Amorphous crystals urine (positive) | 885 | 62 (7.0%) |
| Bacteria urine score | 886 | |
| 0 | 117 (13.2%) | |
| 1 | 255 (28.8%) | |
| 2 | 159 (17.9%) | |
| 3 | 151 (17.0%) | |
| 4 | 204 (23.0%) | |
| Bilirubin urine score | 885 | |
| 0 | 852 (96.3%) | |
| 1 | 11 (1.2%) | |
| 2 | 17 (1.9%) | |
| 3 | 5 (0.6%) | |
| Blood urine score | 880 | |
| 0 | 256 (29.1%) | |
| 1 | 189 (21.5%) | |
| 2 | 154 (17.5%) | |
| 3 | 281 (31.9%) | |
| Glucose urine (positive) | 886 | 63 (7.1%) |
| Ketones urine (positive) | 885 | 115 (13.0%) |
| Leukocyte esterase urine score | 873 | |
| 0 | 76 (8.7%) | |
| 1 | 144 (16.5%) | |
| 2 | 104 (11.9%) | |
| 3 | 549 (62.9%) | |
| Mucous urine score | 885 | |
| 0 | 634 (71.6%) | |
| 1 | 133 (15.0%) | |
| 2 | 43 (4.9%) | |
| 3 | 39 (4.4%) | |
| 4 | 36 (4.1%) | |
| Nitrite urine (positive) | 885 | 328 (37.1%) |
| Urine pH | 887 | 6 (5, 9) |
| Protein urine (positive) | 887 | 557 (62.8%) |
| Red blood cells | 882 | 11 (0, 100) |
| Specific gravity urine | 887 | |
| 1.000 to 1.004 | 31 (3.5%) | |
| 1.005 to 1.009 | 227 (25.6%) | |
| 1.010 to 1.014 | 187 (21.1%) | |
| 1.015 to 1.019 | 162 (18.3%) | |
| 1.020 to 1.024 | 128 (14.4%) | |
| 1.025 to 1.029 | 96 (10.8%) | |
| 1.030 to 1.034 | 48 (5.4%) | |
| ≥ 1.035 | 8 (0.9%) | |
| Trichomonas urine (positive) | 885 | 4 (0.5%) |
| Urobilinogen urine (≥2) | 887 | 173 (19.5%) |
| White blood cell clumps urine (present) | 882 | 205 (23.2%) |
| White blood cells | 877 | 36 (0, 100) |
| Yeast in urine (positive) | 885 | 20 (2.3%) |
| Pregnant | 892 | 12 (1.3%) |
| History of renal failure or dialysis | 892 | 21 (2.4%) |
| History of kidney stones | 892 | 28 (3.1%) |
| Resistance to cefazolin | 831 | 99 (11.9%) |
| Resistance to ciprofloxacin | 892 | 114 (12.8%) |
| Resistance to nitrofurantoin | 853 | 116 (13.6%) |
| Resistance to trimethoprim-sulfamethoxazole | 859 | 147 (17.1%) |
Table 2Evaluation of predictors of resistance to nitrofurantoin.
| Variable | N | Unadjusted analysis | Multivariable analysis | ||
|---|---|---|---|---|---|
|
|
|
||||
| OR (95% CI) | P-value | OR (95% CI) | P-value | ||
| Age (10 year increase) | 853 | 1.03 (0.95, 1.12) | 0.47 | 1.05 (0.95, 1.15) | 0.34 |
| Race (non-White) | 850 | 1.24 (0.84, 1.84) | 0.28 | 1.16 (0.77, 1.75) | 0.49 |
| Marital status | 851 | Overall test of difference: P=0.49 | Overall test of difference: P=0.43 | ||
| Single | 1.00 (reference) | N/A | 1.00 (reference) | N/A | |
| Married | 0.90 (0.55, 1.43) | 0.65 | 0.96 (0.58, 1.56) | 0.87 | |
| Other | 1.23 (0.76, 1.97) | 0.38 | 1.34 (0.81, 2.19) | 0.25 | |
| Primary care doctor | 853 | 1.01 (0.68, 1.50) | 0.94 | 1.02 (0.68, 1.53) | 0.91 |
| Emergency severity index (1 unit increase) | 830 | 0.86 (0.59, 1.23) | 0.41 | 0.94 (0.65, 1.36) | 0.74 |
| Urine specimen source (non-clean catch/void urine) | 670 | 1.42 (0.68, 2.74) | 0.32 | 1.31 (0.62, 2.58) | 0.45 |
| Amorphous crystals urine (positive) | 846 | 1.56 (0.75, 3.00) | 0.21 | 1.53 (0.72, 3.03) | 0.24 |
| Bacteria urine score (1 category increase) | 847 | 0.99 (0.86, 1.14) | 0.85 | 0.97 (0.84, 1.12) | 0.66 |
| Bilirubin urine score (1 category increase) | 846 | 0.76 (0.34, 1.33) | 0.42 | 0.74 (0.32, 1.30) | 0.37 |
| Blood urine score (1 category increase) | 842 | 0.82 (0.69, 0.96) | 0.02 | 0.81 (0.69, 0.96) | 0.02 |
| Glucose urine (positive) | 848 | 1.12 (0.50, 2.24) | 0.76 | 1.12 (0.50, 2.27) | 0.77 |
| Ketones urine (positive) | 846 | 0.68 (0.33, 1.25) | 0.24 | 0.60 (0.29, 1.12) | 0.13 |
| Leukocyte esterase urine score (1 category increase) | 836 | 0.98 (0.81, 1.19) | 0.81 | 1.10 (0.90, 1.36) | 0.37 |
| Mucous urine score (1 category increase) | 846 | 1.22 (1.03, 1.44) | 0.02 | 1.22 (1.03, 1.43) | 0.02 |
| Nitrite urine (positive) | 846 | 0.73 (0.47, 1.10) | 0.13 | 0.68 (0.44, 1.04) | 0.08 |
| Urine pH (1 unit increase) | 848 | 1.07 (0.86, 1.32) | 0.53 | 1.08 (0.87, 1.34) | 0.46 |
| Protein urine (positive) | 848 | 0.79 (0.53, 1.19) | 0.26 | 0.99 (0.64, 1.55) | 0.98 |
| Red blood cells (10 unit increase) | 843 | 0.96 (0.91, 1.02) | 0.23 | 1.01 (0.94, 1.09) | 0.76 |
| Specific gravity urine (1 category increase) | 848 | 0.93 (0.82, 1.05) | 0.26 | 0.87 (0.76, 0.99) | 0.04 |
| Urobilinogen urine (≥2) | 848 | 0.95 (0.56, 1.53) | 0.83 | 0.82 (0.48, 1.35) | 0.45 |
| White blood cell clumps urine (present) | 843 | 0.64 (0.38, 1.05) | 0.09 | 0.69 (0.40, 1.13) | 0.15 |
| White blood cells (10 unit increase) | 838 | 0.99 (0.94, 1.04) | 0.69 | 1.02 (0.96, 1.08) | 0.56 |
| Yeast in urine (positive) | 846 | 1.11 (0.26, 3.38) | 0.87 | 1.12 (0.25, 3.52) | 0.87 |
| Pregnant | 853 | 0.63 (0.03, 3.35) | 0.66 | 0.58 (0.03, 3.18) | 0.61 |
| History of renal failure or dialysis | 853 | 0.70 (0.11, 2.47) | 0.64 | 0.73 (0.11, 2.60) | 0.67 |
| History of kidney stones | 853 | 2.72 (1.03, 6.46) | 0.03 | 3.24 (1.21, 7.90) | 0.01 |
ORs are interpreted as the multiplicative increase in the odds of resistance to nitrofurantoin for each increase given in parenthesis (continuous variables) or presence of the given characteristic (categorical variables). Multivariable models were adjusted for all variables with a p-value <0.10 in unadjusted analysis (blood urine score, mucous urine score, WBC clumps urine, and history of kidney stones). The “Overall test of difference” that is provided for marital status tests whether there is any difference in resistance to nitrofurantoin between the three marital status categories.
OR, odds ratio; CI, confidence interval.