| Congresso Brasileiro de Microbiologia 2023 | Resumo: 329-1 | ||||
Resumo:Food poisoning by Staphylococcus aureus (S. aureus) is one of the most common causes of foodborne illness. This Gram-positive bacteria is considered a superbug that has evolved defense mechanisms for several classes of antibiotics, including penicillin and methicillin. In view of this, innovative food processing technologies are being investigated, such as Photodynamic Inactivation of Microorganisms (PDIM), which allows microbiological decontamination through the combination of a photosensitizer compound (PS), light of adequate wavelength, and molecular oxygen to produce reactive oxygen species (ROS) that cause apoptosis. The objective was to determine the cell viability of S. aureus ATCC 25923 subjected to PDIM-mediated Curcumin (CUR; 1, 7-bis-(4-hydroxy-3-methoxyphenyl)-1, 6-heptadiene-3, 5-dione) in vitro. For this, CUR solutions were prepared under agitation at concentrations of 250, 125, and 62.5 µg/mL with 2.5% dimethylsulfoxide (v/v) for solubilization. The inoculum was standardized at 8 log CFU/mL. 100 μL aliquots of standardized bacterial suspension were inoculated into 900 μL of test solutions. The samples remained in the dark for 10 min before being illuminated by a blue light emitting diode (λmax = 450 nm) with exposure of 5 min, resulting in a total energy dose of 0.81 cm-2. To control light and the action of PS in the dark, suspensions of microorganisms were irradiated in the absence of PS and the stock solution was tested without irradiation. Serial decimal dilutions of samples were made for inoculation onto Mannitol Salt Agar plates. Plates were incubated at 37°C/48 h and cell viability results were expressed in log CFU/mL. The application of light without PS inhibited approximately 0.6 log CFU/mL of microorganisms. This is due to the presence of metabolites naturally produced by bacteria that act as endogenous PS, as they have a visible light absorption band and produce ROS, as well as exogenous PS. CUR expressed its antimicrobial activity with dark toxicity, reducing 1.09 log CFU/mL at a concentration of 125 µg/mL. Lower cell viability was observed in illuminated samples (2.1 ± 2.3 log CFU/mL) when compared to samples without photoinactivation (6.4 ± 0.5 log CFU/mL). Drug concentration interfered with inactivation efficiency, with greater reductions for higher concentrations. The combination of 62.5 µg/mL CUR and illumination inactivated 100% of the inoculum (S. aureus 7 log CFU/mL). Photoinactivation occurs when PS excited by light transfers electrons and protons to adjacent molecules, forming radicals that react with molecular oxygen to produce superoxide anions, hydroxyl radicals, and hydrogen peroxide (type I reaction), or transferring energy to molecular oxygen and the formation of singlet oxygen (type II). ROS lack specific targets, so they initiate various death signaling pathways by oxidizing critical intracellular components such as DNA, RNA, enzymes, membranes, and lipids. This rapid and non-specific action makes the development of resistance unlikely, as there is no time for a cellular response to oxidative stress and it does not depend on the keyhole principle of antibiotics. Therefore, CUR exhibits dark toxicity and synergistic antimicrobial activity against S. aureus when used in PDIM, making this technique a promising alternative to eliminate foodborne pathogens and prevent the development of multidrug resistance in microorganisms. Palavras-chave: food preservation, foodborne pathogens, innovative food processing technologies, microbiological decontamination , multidrug resistance Agência de fomento:Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) | |||||