Potencial terapêutico do extrato padronizado de própolis (EPP-AF®) no tratamento da sepse induzida por Escherichia Coli patogênica extra intestinal

Abstract

Sepsis represents a serious public health problem worldwide, with a high mortality rate and complex treatment. This syndrome can be triggered by several pathogens, such as extra-intestinal pathogenic Escherichia coli strains (ExPEC) capable of producing serine proteases, such as the protein involved in colonization (Pic). Several biological roles for Pic have already been described, including the ability to cause lethal sepsis. The need to contain the evolution of the infection in patients affected by sepsis has stimulated research centers in the discovery of therapeutic targets aimed at the immune system for an effective and safe host response. In this context, propolis can represent a therapeutic alternative due to its multiplicity of applications and biological properties. The objective of this work was to investigate the therapeutic potential of standardized propolis extract (EPP-AF®) in the treatment of sepsis induced by extra intestinal pathogenic Escherichia coli. For this, in vitro tests of macrodilution in broth and time-to-death curve were performed to verify the antimicrobial activity of EPP-AF®. In vivo assays were also performed to evaluate the potential of EPP-AF® to control sepsis induced by E. coli F5. For this, Swiss mice aged between 6-8 weeks were infected with E. coli F5 and treated with EPP-AF® prophylactically and therapeutically, at doses of 200 mg/kg and 400 mg/kg. After infection and treatment, the survival of the animals was followed for 5 days. After determining the treatment that maintained the highest survival rate, the infection and treatment procedures were repeated for the collection of biological material for the quantification of Colony Forming Units (CFU), serum dosages, cellular quantification and histopathological evaluations. The minimum bactericidal concentration (MBC) of EPP-AF® was 16 mg/mL, with bactericidal action in the first 30 minutes after incubation at a concentration of 20 mg/mL. The animal survival showed that the prophylactic treatment with EPP-AF® was more effective, and doses of 200 and 400 mg/kg kept the animals alive until the end of the experiment, at rates of 50% and 33%, respectively. EPP-AF® 200 mg/kg reduced the number of CFUs in the initial site of infection (peritoneal cavity) and in the liver, while the dose of 400 mg/kg reduced the number of CFUs in the lung. The extract did not induce histological changes in the organs of the treated animals or in the amount of red blood cells, platelets or plasmatic proteins. Treatment with EPP-AF®, however, altered the serum profile of leukocytes in septic animals. There was a significant increase in the number of lymphocytes and monocytes, and a reduction in neutrophils in the infected group and treated prophylactically with EPP-AF® 200 mg/kg when

compared to the infected group. The infected and treated prophylactically with EPP- AF® 200 mg/kg group also showed an increase in peritoneal cells compared to the

infected group, which may have contributed to the reduction of CFUs in the peritoneum. Thus, the results of this study show the therapeutic potential of the standardized extract of propolis (EPP-AF®) in the treatment of sepsis, being able to reduce the number of bacteria and increase the survival of septic animals by modulating the immune response.