Experimental evaluation of the effect of porphyrins in antimicrobial photodynamic inactivation of burn wounds

Objective. To studyandevaluate the effect of porphyrinson the microbialcontamination of infectedburnwounds in experimentalanimalsduringantimicrobialphotodynamicinactivation(PDI).

Materials and methods. Objects: asymmetric water-soluble porphyrins containing heterocyclic fragments on the periphery of the porphyrin cycle: benzoxazole residues (O-por), N-methyl benzimidazole (N-por) and benzothiazole (S-por). Animals: white mongrel Wistar rats weighing 250-300 g. (males, n=20), which received a III-degree contact burn contaminated with a test strain of S. аureus ATCC 29213. All animals are divided into four groups: No. 1 - PDI with O-por (n=5); No.2 – PDI with S-por (n=5); No. 3 – PDI with N-por (n=5); No. 4 (control) – PDI with 0.9% sterile sodium chloride solution (n=5). PDI parameters: LED light source (white light), maximum power: 20 W, maximum luminous flux: 1500-1800 lm, photo-irradiation time: 10 minutes. Two PDI sessions were conducted. Microbial contamination of wounds was studied in microbiological examination of wound discharge. The results of the microbiological study were qualitative (isolation of the causative agent of infection, its identification) and quantitative (determination of the number of colony-forming units (CFU/ml)). To evaluate the effectiveness of PDI, the values of the coefficient of logarithmic decrease in CFU of isolated microorganisms were calculated. Statistical data processing was performed in the R 4.2.1 environment (Rstudio 1.1.463).

Results. There was a decrease in the titer of microorganisms after the first and second sessions of PDI for all the studied compounds. The change in wound contamination towards pathogen clearance on the first day of the experiment was statistically significant for all porphyrin compounds tested (O-por p=0.0126;
S-por p=0.0377; N-por p=0.0128)comparedwith the controlgroup.According to the indicator, allthreetypes of porphyrinsshowed an efficiency of ≥90%.Thelogarithmicdecrease in CFUrangedfrom1to2dependingon the porphyrincompound,whichcorresponds to the inactivationof90to99% of microorganismsin the biomaterial.

Conclusions. The largest and statistically significant decrease in the number of microorganisms was observed in the groups of animals in which photosensitizers with heterocyclic fragments of benzimidazole
(N-por) and benzothiazole (S-por) were used, the indicators of logarithmic decrease in CFU was 2 (p=0.0065) and 1.3 (p=0.0232), respectively.