Background: : Proteus mirabilis (PM) as well as other membersof the Enterobacteriaceae family are a leading cause ofinfectious diseases in both the community and acute caresettings. The prevalence of multi-drug resistant (MDR) bacterialisolates have increased in the last few years, affectingthe prognosis and survival of hospitalized patients. The aimof our study was to determine the risk factors and clinicaloutcomes of urinary tract infections (UTIs) caused by MDR PMin patients hospitalized in our institution. Methods: : This was a retrospective matched case-controlstudy. Records of patients with PM-positive urine culturewere reviewed, and data were included for analysis. Results: : Univariate analysis revealed that the variablessignificantly associated with acquisition of MDR PM vs non-MDR PM UTI were younger age ([in years] median 77.5,range 20-94 vs median 78, range 40-94, p = 0.04), otherconcomitant infectious diseases (57.1 vs 35.7%, p = 0.037),number of prior infectious diseases (mean 0.95 ± 0.99 vs0.57 ± 0.85, p = 0.035), diagnosis of infection at hospitaladmission (67.9 vs 42.9%, p = 0.008), and prior therapywith antipseudomonal penicillin (17.9 vs 1.8%, p = 0.004),respectively. Mean length of hospitalization was 29.95 daysfor the MDR group and 30.04 days for the non-MDR group(p = non-significant [NS]). The crude mortality rate followinghospital admission was 19/56 (33.9%) vs 14 (25%)in the MDR PM and non-MDR PM groups, respectively(p = 0.300, odds ratio [OR] 1.54, 95% confidence interval[CI] 0.63-3.82). The production of extended-spectrum betalactamases(ESBL) was found in 100% of MDR-PM vs 31.5%of non-MDR-PM urine isolates (p < 0.001). All variablesfound to be significantly associated with MDR-PM UTI wereincluded in a logistic regression model. Independent riskfactors for MDR-PM UTI were empiric cephalosporin therapy(OR 4.694, 95% CI 1.76-12.516, p = 0.002) and prior antipseudomonalpenicillin (piperacillin/tazobactam) therapyduring the last year (OR 11.175, 95% CI 1.09-114.2,p = 0.04). Conclusions: : Prior piperacillin/tazobactam and empiriccephalosporin use were the independent risk factors ofMDR-PM strains. All MDR-PM urinary isolates at our institutionwere ESBL producers. Therefore, carbapenem useremains the only available treatment option for MDR-PMisolates in our institution.