Caracterização de kefir de leite e impacto do seu consumo em modelo murino de infecção por Salmonella Typhimurium

Abstract

ABSTRACT Due to the global problem of antimicrobial resistance in bacteria, and the lack of success and investment in research looking for new antibiotics, new effective alternatives are needed to reduce bacterial infections. The World Health Organization warns that diseases transmitted by contaminated food (Foodborne diseases) kill 420,000 people worldwide per year and one in ten people in the world become ill after ingestion. Among Foodborne diseases, bacteria of the genus Salmonella are the second major cause of infections in Brazil. A possible solution is the use of probiotics, which are foods with viable microorganisms capable of conferring health benefits when administered in predetermined doses. Kefir, a probiotic originating in the Caucasus and the Balkan Peninsula, is a fermented food, in milk or water, whose alcoholic and lactic fermentation is carried out by kefir grains or kefir yeast. This product has antimicrobial, anti-inflammatory and antioxidant activities; assists in the treatment of inflamed bowel syndrome and diarrheal diseases. In this work, the microbiological and physical-chemical characterization of a kefir-fermented milk drink produced in domestic conditions was carried out (25°C ± 2°C for 24 h, without agitation in an aerobic environment), as well as its consumption by C57BL/6 mice and the relationship with the intestine-brain axis. This axis describes the participation of both organs in continuous and bidirectional communication. New technologies made possible to demonstrate that digestive stimulation can activate regions of the brain, just as psychological symptoms can cause disturbances in gastrointestinal function. Furthermore, the effect of Kefir consumption in this murine model before the challenge with Salmonella enterica subs. enterica Typhimurium. All experiments were accompanied by metagenomic analysis to characterize the bacterial community under the evaluated conditions. The relative abundance was calculated and, initially, it was observed that animals treated with Kefir had a higher relative abundance of bacteria from the Lachnospiraceae family and the genus Lachnoclostridium, and a lower relative abundance of enterobacteria such as Helicobacter and Shigella/E.coli. Some benefits previously associated with the use of kefir were also found, such as an increase in the production of butyrate and an increase in the activity of enzymes that participate in the anti-oxidative process. However, given the infection, animals fed with Kefir showed higher mortality than animals treated with water (control group), associated with inflammatory effects (there was an increase in IFN-ɤ and a decrease in IL-10) that compromised the infection control, leading to a lack of immune response, allowing Salmonella typhimurium to cause a severe infection. Thus, the indiscriminate use of probiotics, especially in cases of infections, should be used with caution, as they may also be associated with toxic or unwanted effects.