CC BY
2The 30th International Conference on Advanced Laser Technologies B-O-16
ALT'23
Efficacy of photodynamic therapy against uropathogenic bacteria
V. Elagin1*, N. Ignatova2, A. Antonyan3, I. Budruev4, P. Bureev4, O. Streltsova3, V.
Kamensky15
1Institute of Experimental Oncology and Biomedical Technologies, Privolzhsky Research Medical University, Russia 2Department of Epidemiology, Microbiology and Evidence-Based Medicine, Privolzhsky Research Medical University,
Russia
3Department of Urology Named after E. V. Shakhov, Privolzhsky Research Medical University, Russia 4Institute of Biology and Biomedicine, Lobachevsky State University of Nizhny Novgorod, Russia 5Federal Research Center Institute of Applied Physics of the Russian Academy of Sciences, Russia
It is well known that from 30% to 51% of urinary calculi are infected or have a bacterial origin. Modern lithotripsy approaches are based on crushing stones into small fragments that can be removed/washed out through small diameter accesses. In the case of infected stones, large amount of toxins and bacteria are inevitably released during fragmentation. Antimicrobial photodynamic therapy is considered to be an alternative to the antibiotic treatment of localized infectious processes. The purpose of the study was to evaluate the antibacterial efficacy of photodynamic therapy against human antibiotic-resistant bacterial uropathogens.
Uropathological microorganisms were isolated from renal calculi. It was found that 78.7±5.2 % of renal calculi were contaminated. Testing the sensitivity of the isolated strains to 10 antibiotics of different mechanisms of action showed that the studied strains have a high antibiotic resistance. The interaction between photosensitizer and urapothogenic microorganisms was analyzed. Since the samples were washed from free molecules of photosensitizer, the fluorescence was only detected from the photosensitizer that had penetrated into cells and/or was bound with cell wall. The photosensitizer accumulation was estimated to be dependent on both incubation time and concentration. The fluorescence intensity was found to be higher for Gram-negative strains than for the Gram-positive ones regardless of the photosensitizer concentration. The strains of Enterococcus faecalis and Staphylococcus aureus demonstrated the enhancement of the fluorescence intensity in a time-dependent manner with the maximal value at 60 min. Escherichia coli and Proteus mirabilis had the maximal value of fluorescence intensity after 30 min and that significantly decreased by 60 min. The optimal incubation time was found to be 30 minutes. However, this technique is planning to use during laser lithotripsy for sanitation, where the time is a limiting factor; therefore, 15 min of incubation was chosen. The concentration of the photosensitizer was selected to be 50 ^g/mL. After 15 minutes of incubation in the dark followed by 15 minutes of manipulation (dilution, inoculation) at ambient light, no colony of S. aureus and E. faecalis was detected on the plates. The treatment of either Gram-positive or Gram-negative bacteria by laser light only did not induce significant reduction of CFUs. The survival rate of P. mirabilis for antimicrobial photodynamic therapy (aPDT) was power-dependent. The number of viable bacteria was decreasing from 65% to 10% with an increase in power from 50 mW to 150 mW. The maximal bactericidal effect was reached at 150 mW.
Next, the aPDT was adapted for Gram-negative species. The efficacy of aPDT of E. coli incubated with photosensitizer and Triton X-100 achieved 52.5%. It was found that washing of the extracellular photosensitizer led to loss of the aPDT efficacy. The high sensitivity of P. aeruginosa to aPDT with extracellular photosensitizer significantly reduced after washing of the photosensitizer. The efficacy of aPDT of P. mirabilis did not change after washing of the extracellular photosensitizer. It was demonstrated that the aPDT efficacy depended on laser power in all studied species, excluded K. pneumoniae. The efficacy of K. pneumoniae treatment did not exceed 93%. The irradiation of other bacteria species with a power of 450 mW provided an aPDT efficacy of 99.99%. To test the efficacy of the developed aPDT technique, urine cultures of the patients were incubated with a photosensitizer and Triton X-100 for 15 minutes in the dark. Then, the unwashed samples were illuminated by a continuous wave laser at 450 mW of output power. The efficacy of the aPDT of infected urine cultures was not less than 99.996%. This work was supported by the Russian Science Foundation, project №21-15-00371.
