Objective:To investigate the characteristics of distribution and drug resistance of urinary bacteria in the mid-stream urine of patients with infectious stones.Methods:The retrospective study analyzed the clinical data of 254 patients with infectious stones in the First Affiliated Hospital of Guangzhou Medical University from September 2016 to September 2018. All patients were treated with PCNL. Overall, there were 101 male and 153 female patients, with the mean age of(51.5±12.3) years, and the mean stone burden of 1443.5(660.8, 2837.5) mm2. There were 58 (22.8%) patients with hypertension, 17(6.7%) patients with diabetes and 195(76.8%)with hydronephrosis. The mid-stream urine samples were obtained for bacterial culture and susceptibility test, and the results of urine culture and antimicrobial susceptibility were recorded and analyzed.Results:Of 254 patients involved in this study, 89(35.0%) were positive and 165 (65.0%) were negative for urinary bacterial culture of the mid-stream. The proportion of patients with positive urine bacterial culture of the mid-stream who had positive urine leucocytes, positive urine nitrite and postoperative pyrexia were 86.5%(77/89), 64.0%(57/89), 25.8%(23/89), respectively, which was higher than that of patients with negative urine bacterial culture of the mid-stream [50.3%(83/165), 14.5%(24/165), 14.5%(24/165), P<0.05]. Four teen kinds of bacteria were detected from the mid-stream urine, and the three bacteria with the highest detection rate in turn were Escherichia coli of 38.2%(34/89), Proteus mirabilis of 15.7%(14/89), and Pseudomonas aeruginosa of 11.2%(10/89). The results of this study showed that three common bacteria had high resistance to drug including Cefazolin, Cefuroxime, Cefuroxime ester, Ampicillin and Co-trimoxazole (all resistance rate>40%). The resistance rates of Escherichia coli and Pseudomonas aeruginosa to Ciprofloxacin and Levofloxacin were higher than or equal to 40%. The resistance rates of Escherichia coli and Proteus mirabilis to meropenem, imipenem, ertapenem, piperacillin/tazobactam and amikacin were all lower than 10%. In addition, the resistance rates of Escherichia coli to nitrofurantoin and tigecycline and Proteus mirabilis to tobramycin, aztreonam and cefoxitin were all less than 10%. The resistance rates of Pseudomonas aeruginosa to ceftazidime, cefepime, gentamicin and aztreonam were less than 10%. Conclusions:The highest detection rate of urinary bacteria in culture of the mid-stream with infectious stones are Escherichia coli, Proteus mirabilis and Pseudomonas aeruginosa, all of which showed high resistance to Ampicillin, Cotrimoxazole, and some cephalosporins. Escherichia coli and Pseudomonas aeruginosa showe high resistance to Ciprofloxacin and Levofloxacin, and all of the three bacteria have low resistance rates to some β-Lactamase inhibitor complex and carbapenems, suggesting a reference for clinical empirical medical treatment.