Terapia fotodinâmica antimicrobiana no tratamento de infecção sistêmica em modelo experimental de Galleria Mellonella

Abstract

Infections caused by Staphylococcus aureus are particularly difficult to treat due to the high rate of resistance to antibiotics. They are opportunistic pathogens and important hospital strains that can cause illnesses ranging from mild to severe, and can lead to death. Antimicrobial Photodynamic Therapy (aPDT) is a promising alternative model, with antimicrobial properties, dependent on three factors: light, light-sensitive photosensitizing agent and environmental oxygen molecules. The objective of this study was to evaluate the antibacterial action of aPDT in the treatment of systemic infection in an experimental model of Galleria mellonella. The study was experimental in vivo, with direct observation in the laboratory. Planktonic forms of S. aureus were prepared in lethal concentrations, and G. mellonella were divided into 6 experimental groups and each group had 10 larvae. For each of the forms after infection with: aPDT; Red laser; Methylene Blue; Ceftriaxone; Ceftriaxone + aPDT; NaCl 0.9%. After determining the infection and treatment, the larvae were observed after the first 4 hours and, subsequently, at intervals of 24 hours, for 120 hours, to evaluate the survival curve. Subsequently, 3 larvae from each group were randomly chosen, macerated, homogenized and diluted for plating. The plates were incubated for 24 hours and the amount of CFU was counted. Super infection was found in the inoculum of 109. After observing the samples from each group, the results found showed that for the survival curve, the best results were obtained from the combined therapy between ceftriaxone and TFDa, with better survival rates. All treatment groups demonstrated cell reduction when compared to the control group, with NaCl 0,9%. Therefore, the results point to a potential in vivo bactericidal effect of TFDa in S. aureus infection.