Assessment of the Effect of Antimicrobial Photodynamic Therapy on Multidrug- Resistant Acinetobacter baumannii Strain Biofilm - an in Vitro Study

Acinetobacter baumannii is an opportunistic bacterium associated with numerous cases of hospital-acquired infections and possesses, among other characteristics that make it virulent, resistance to various antibiotics. The increasing resistance of microorganisms has led to the search for alternative methods, such as Antimicrobial Photodynamic Therapy (aPDT), inducing bacterial cell death. This study aimed to evaluate the antimicrobial action of PDT with curcumin on A. baumannii biofilm in vitro. A. baumannii biofilm was treated with curcumin for 20 min and then irradiated with a 450 nm LED (Light Emitting Diode) at 93.9 mW/cm2, with a fluence of 42.72 J/cm2. Subsequently, tests were conducted using Confocal Microscopy with the Resazurin dye, Colony-Forming Units (CFU) counting, and Scanning Electron Microscopy (SEM) imaging. Cell viability tests were also conducted using the L929 fibroblast cell line. The results show that although PDT with curcumin did not reduce bacterial growth, it caused alterations in cell metabolism. Additionally, confocal microscopy showed that curcumin was internalized by A. baumannii at the concentrations used. SEM demonstrated structural changes, although no bacterial reduction in the biofilm was observed. The parameters used in biofilm treatment were cytotoxic to L929 cells. This study showed that PDT with curcumin induces fragility in A. baumannii cells, suggesting that a possible combination with antibiotics may lead to the elimination of bacterial infection.