Fusobacterium nucleatum (ATCC 25586) is an obligate anaerob, gram negative, non-spore former, and pleomorphic bacillus that can cause brain, pleura, lung and liver diseases mainly in the mouth and teeth. It was also noted that F. nucleatum induces fetal death (fetal demise) in pregnant women. Recent studies implicated that F. nucleatum could lead to colon cancer by binding the epithelial tissue. Kefir is originally produced from kefir grains that are actually a mine of probiotics. Fermented dairy products especially kefir and yogurt are significant for functional nutrition. Lactic acid bacteria, acetic acid bacteria and yeasts are embedded in a polysaccharide matrix, called kefiran, in kefir grains. When kefir grains are added to milk and incubated for approximately 22 h at 25°C, microorganisms in the grains continue to proliferate in milk with the production of the functional metabolic compounds. While yogurt has mainly two bacteria, authentic kefir has its characteristic Lactobacillus kefiranofaciens, Lactobacillus kefir and Lactobacillus parakefir in addition to many other types of LAB. Previous studies have indicated that fermented dairy products can cause probiotic effects such as improvement in digestive system health, serum cholesterol reduction, and improvement in lactose tolerance, improved immune function, control of irritable bowel symptoms, as well as anticarcinogenic properties.The aim of this research is to study in vitro the growth of F. nucleatum with fermented dairy products known to have a positive effect on intestinal health and so to investigate the possible inhibition effect of dairy products on this microorganism that is directly related to intestinal cancer. The effect of microflora and metabolites of kefir, yogurt and milk samples against to F. nucleatum were determined with various methods (microflora formation after fermentation, zone inhibition). Kefir samples exhibited distinct inhibitory zone against F. nucleatum after incubation agar plates. In addition, both probiotic bacteria and related pathogen were enumerated after fermentation by adding a certain amount of F. nucleatum pure culture to kefir and yoghurt samples. It was found that number of F. nucleatum decreased depending on kefir and yoghurt concentration produced from kefir grains.Kefir is known to have positive effects on health, especially intestinal health; therefore, these findings are important since inhibition effect of fermented dairy products against a pathogen and possible carcinogen was shown. Regular consumption of natural fermented dairy products especially kefir should be included in a functional diet. It could be promising to investigate with in vivo studies.?Keywords: Fuscobacterium nucleatum, pathogen, carcinogen, kefir, kefir grains, antimicrobial, anticancerogen
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