Aim. To define persistent properties and antibiotic resistance of microorganisms isolated from the urine of adult patient undergoing surgery for urolithiasis.
Materials and methods. Urine specimens were obtained from the renal pelvis and urinary bladder during percutaneous nephrolithotripsy. Microorganisms that were isolated from the urine were examined for their persistent properties (anti-lysozyme activity, the ability of biofilm formation) and antibiotic resistance using photometric and bacteriological methods.
Results. Strains of microorganisms isolated from the urine of patients with urolithiasis have high anti-lysozyme activity and the ability of biofilm formation, and variable antibiotic resistance. These properties should be taken into account when selecting an empirical antibiotic therapy for preventing infectious-inflammatory complications after percutaneous nephrolithotripsy.
Conclusion. The high level of resistance of microorganisms isolated from the urine of patients with urolithiasis to the studied antibiotics, their ability to inactivate lysozyme and form biofilms may be the cause of the development of postoperative complications.

Keywords: persistent properties, microorganisms, antibiotic resistance, urolithiasis