Multidrug-Resistance Patterns and Predictors in Adult Acute Pyelonephritis: A Three-Year Cohort from a Tertiary Romanian Center with Derivation of the PYELO-MDR-Risk Score.

Background and Objectives: Multidrug-resistant (MDR) uropathogens are reshaping the empirical management of acute pyelonephritis, particularly in Eastern European centers. We aimed to describe MDR patterns, identify admission-level predictors, including renal impairment/renal-failure status at presentation and major healthcare exposure variables, and derive a bedside risk score (PYELO-MDR-Risk) for adult pyelonephritis at a Romanian tertiary hospital. Methods: We retrospectively analyzed 129 consecutive culture-confirmed acute pyelonephritis admissions at "Victor Babeș" University Hospital, Timișoara (March 2022-March 2025). MDR was defined as non-susceptibility to ≥1 agent in ≥3 antimicrobial categories. We compared MDR and non-MDR cases on demographics, microbiology, time-to-effective therapy (TTE), and outcomes; multivariable logistic regression identified independent predictors and was the basis for a points-based score with bootstrap-based internal validation (1000 resamples). Results: Fifty-four patients (41.9%) had MDR pyelonephritis. Escherichia coli remained the dominant uropathogen (55.8%) but was less prevalent in the MDR group (40.7% vs. 66.7%; p = 0.003), whereas Klebsiella pneumoniae and Pseudomonas aeruginosa were enriched. Independent predictors of MDR were antibiotic exposure ≤90 days (aOR 5.7, 95% CI 2.4-13.6), recurrent UTI (aOR 3.4, 1.4-8.2), recent hospitalization (aOR 3.1, 1.2-8.0), and renal impairment/renal-failure status at admission (aOR 2.4, 1.0-6.2). Immunosuppression, prior urinary tract instrumentation, and nephrolithiasis/urolithiasis were evaluated as candidate predictors but did not independently improve the final point score after adjustment. MDR was associated with delayed effective therapy (28.4 vs. 9.7 h; p < 0.001), longer hospitalization (13.7 vs. 8.9 days; p < 0.001), and higher 30-day readmission (20.4% vs. 8.0%; p = 0.038). The PYELO-MDR-Risk score (range 0-12) achieved an optimism-corrected AUC of 0.84 with adequate calibration (Hosmer-Lemeshow p = 0.624). Conclusions: MDR drives a substantial fraction of pyelonephritis admissions in Western Romania and tracks closely with prior antibiotic and healthcare exposure. The PYELO-MDR-Risk score offers a transparent bedside tool for empirical-therapy decisions in the local setting, pending national and international external validation.