['Multidrug resistant (MDR) uropathogens are increasing in prevalence and may contribute to significant morbidity after percutaneous nephrolithotomy (PCNL). We investigate the presence of MDR bacteriuria and occurrence of postoperative infectious complications in patients who underwent PCNL at our institution.', 'Retrospective review was performed of 81 patients undergoing PCNL by a single surgeon (RLS) between 2009 and 2013. Patient demographics, comorbidities, stone parameters on imaging, and microbial data were compiled. MDR organisms were defined as resistant to three or more of the American Urological Association Best Practice Statement antimicrobial classes for PCNL. Postoperative complications were graded by Clavien score and European Association of Urology infection grade. Univariate comparisons were analyzed between patients with and without a postoperative infectious complication. Multivariate logistic regression was performed to determine significant predictor variables for postoperative infectious complications.', 'Of the 81 patients undergoing PCNL, 41/81 (51%) had positive preoperative urine culture, 24/81 (30%) had positive MDR urine culture, and 16/81 (19%) had a postoperative infectious complication. Multivariate analysis revealed a positive preoperative MDR urine culture significantly increased the risk of postoperative infectious complication (odds ratio [OR]=4.89, 95% confidence interval [CI] 1.134-17.8, P=0.016). The presence of more than one access tract during PCNL also predicted for infectious complications (OR=7.5, 95% CI 2.13-26.4, P=0.003) Of the 16 patients with a postoperative infection 3 (18%) had postoperative urine cultures discordant with the preoperative urine cultures.'] Does multidrug resistant bacteriuria before percutaneous nephrolithotomy predict for postoperative infectious complications?