Introduction. Since the results of treatment of chronic pyelonephritis (CP) depend on timely and rationally selected targeted antibiotic therapy, when choosing a treatment regimen, it is necessary to rely on the local data obtained by monitoring the state of microflora in a particular hospital.
Aim: to monitor the changes in urine microflora in patients with urinary stone disease.
Materials and methods. A total of 598 isolated bacteria and yeast-like fungi from patients with urinary stone disease who were treated in the Department of Urology during different time periods (1997–1999, 2010–2014 and 2015–2017 yy) were analyzed. A comparison of the urine microbiota in patients with single kidney stone (n=154) and staghorn stone (n=147) for the period 2015–2017 yy. was carried out.
Results. The significant changes of gram-positive and gram-negative bacteria were found with a tendency to decrease in the proportion of the latter (from 80.6% to 50.6%, p<0.05) due to a decrease in the proportion of P. mirabilis and complete absence of Enterobacter spp, Serraciae spp and Citrobacter spp. as well as an increase in the number of gram-positive bacteria (from 18 to 48.7%, p<0.05) owing to increase in the proportion of E. faecium + E. faecalis. During observation period, E. Coli has remained the leading pathogen (26.4±0.32%).
During observation period, a permanent fourfold prevalence of gram-negative bacteria in clinically significant concentrations (>104 CFU/ml) was found: E. coli (36.8±4.1%). The proportion of K. Pneumonia increased from 8.5% to 17.4%, and proportion of P. mirabilis decreased from 20.3 to 10.4%. Despite a significant increase in the proportion of Enterococcus spp. (from 4.6 to 26.6%) in the general population, the incidence of microorganisms in clinically significant concentrations during analyzed period remained unchanged and did not exceed 8.46±4.76%. In patients with single stones and patients with staghorn stones there was no significant difference in the proportion of analyses with clinically significant concentrations of bacteria fer (p>0.05). The percentage of analyses with clinically significant concentration was 70.06%, while in all patients with urolithiasis it was 59.7%.
In patients under and over 60 years old, the largest number of bacterial pathogens were represented by E. coli. (29.7% and 32.1%, respectively).
Conclusion. E. Coli remains the leading bacterial causative agent of calculous pyelonephritis, both in the general population and in analyses with clinically significant concentrations of bacteria. There were no significant differences in urine microflora in patients with staghorn and single stones.

Keywords: change of urinary flora, urinary stone disease, chronic pyelonephritis