Investigation of the potential probiotic effects of lactic acid bacteria and cell-free supernatants against important pathogens leading to wound infections

Probiotic lactic acid bacteria stimulates the production of defense cells and thereby help the healing of wounds. It can also be effective in antimicrobial and antibiofilm activity against many pathogenic bacteria. In this study, it was aimed to evaluate the antimicrobial effects of 12 lactic acid bacteria active cultures and cell-free supernatants isolated from various fermented milk products against Pseudomonas aeruginosa and Staphylococcus aureus, as well as the inhibitory effects of cell-free supernatants on the biofilm formation of pathogens. Active cultures were evaluated by agar spot and cell-free supernatants were evaluated by the agar-well diffusion method. As for biofilm experiments the quantitative-microdilution plate method was used. It was determined that isolates were Pediococcus parvulus (8.3%, 1/12), Lactobacillus paracasei (16.7%, 2/12), Leuconostoc mesenteroides (16.7%, 2/12), Lactobacillus coryniformis (8.3%, 1/12), Lactobacillus reuteri (16.7%, 2/12), Lactobacillus rhamnosus (8.3%, 1/12), Lactobacillus alimentarius (8.3%, 1/12), Lactobacillus delbrueckii (8.3%, 1/12) and Lactococcus lactis (8.3%, 1/12) species by 16S rRNA PCR analysis. Antibiotic susceptibility profiles of the isolates were evaluated by the E-test method and it was determined that they were sensitive to selected antibiotics. According to the findings of antimicrobial activity, the inhibition effects of active culture and cell-free supernatants (HS-72) of L. delbrueckii subsp. bulgaricus strain ND04 and L. mesenteroides subsp. mesenteroides strain CAU4374 were evaluated to be only similar to P. aeruginosa strains among the pathogenic bacteria. Three separate applications performed with cell-free supernatants and the highest biofilm inhibition rate was determined for each pathogen. Accordingly, as a result of incubation of HS-72 with the pathogen, the following highest inhibition rates were recorded; 96.0% and 95.7% (L. lactis strain IL6288) for P. aeruginosa ATCC 15692 and P. aeruginosa ATCC 27853, 94.2% (L. reuteri strain SKB1241) for S. aureus ATCC 35556 and 96.2% (L. paracasei strain RV-M192) for S. aureus ATCC 6538. Inhibition effects are thought to be caused by organic acids in antimicrobial activity experiments, and other inhibitory substances in supernatants in biofilm experiments. Considering that biofilms formed by P. aeruginosa and S. aureus pathogens are important problems in the treatment of chronic wounds, it is thought that new findings in which the cell-free supernatants of lactic acid isolates inhibit biofilm formation of pathogens and destruct the generated biofilms will greatly contribute to the scientific literature. Keywords: Biofilm, cell-free supernatant, lactic acid bacteria, wound infections.