Photodynamic inactivation (PDI) is considered to be an effective method of prevention of postoperative complications of urolithiasis. The present study shows a complex approach to assess the efficacy of PDI of drug resistant bacteria associated with renal calculi. Bacterial strains associated with renal calculi were isolated and identified using standard methods of bacteriological analysis and tested for drug resistance to 10 antibiotics by the disco-diffusion method. Uropathogenic bacterial strains present in 78.7 ± 5.2% of the infected samples from the total number of analyzed calculi. The most frequent representatives belonged to the genera Staphylococcus, Escherichia, and Enterococcus. All tested strains showed high antibiotic resistance. Representatives of the most common bacterial genera in the calculi were used as models for the selection of PD exposure modes. It was found that the maximum time of photosensitizer accumulation depends on the structure of the bacterial cell wall: 30 min for Gram-negative strains and 60 min for Gram-positive ones. Optimal modes of PD exposure to antibiotic-resistant uropathogenic microorganisms were selected: 50 µg/mL Fotoditazin and 150 mW laser power. The maximal bactericidal activity of PDI against uropathogenic microorganisms was shown for Enterococcus faecalis, and Staphylococcus aureus. The bacteriostatic effect was found against Escherichia coli and Proteus mirabilis.

Due to the prevalence of postoperative complications in the treatment of urolithiasis, the study of the contamination of urinary calculi and the potential pathogenicity of isolated bacteria is of great importance in laboratory diagnostic practice. It has been shown that uropathogenic bacteria are found in the composition of urinary stones in 65±7.1% of cases, mainly representatives of the Enterobacteriaceae and Staphylococcaceae families. Bacteria of the generas Escherichia, Enterococcus, Staphylococcus were most frequently detected. The analysis of biofilm activity and antibiotic resistance in 50 uropathogenic strains was carried out. It was shown that all the studied strains were resistant to at least two tested drugs, and the average value of the multiple resistance index was 0.51. When cultured on nutrient agar with Congo red, it was shown that more than half of the tested strains have high biofilm activity and about 80% potential for biofilm formation. The greatest biofilm activity was observed in bacteria of the generas Escherichia, Klebsiella, Enterobacter, Staphylococcus.