EN
INTRODUCTION: The ketogenic diet (KD) is high fat and low carbohydrate diet type. Ketogenic metabolism is characterized by moderate hypoglycemia. It also leads to the use of ketone bodies as an alternative source of energy for the organism. In the last decade, the influence of various factors on the gut microbiota has been noticed. The gut microbiota includes bacteria as well as fungi, archaea, viruses, and protozoa. Gut microbiota has been shown to participate in the regulation of processes in the central nervous system via the gut-brain axis. Differences in the composition of gut microbiota can affect the proper functioning of the central nervous system. It seems that KD can affect the gut microbiota composition. AIM(S): The aim of the study was to evaluate the influence of two types of KD high in animal fat on the number of Enerococcus faecalis and Escherichia coli in faeces of 129SV mice. METHOD(S): Ten male 129SV mice were divided into two groups and fed for 28 days with a KD high in animal fat with different ratios (4: 1 and 6: 1). The assessment of the number of bacteria was performed on 0, 14, and 28 days of feeding with the KD by real time‑QPCR. Additionally, body mass and β‑hydroxybutyrate levels were measured. RESULTS: An increase of the amount of Enterococcus faecalis and Escherichia coli after 14 and 28 days in the faeces of 129SV mice fed with both KDs was observed. The results showed a decrease in the body mass of mice fed with KD with ratio of 4: 1. Changes in body mass of mice fed with KD with a ratio of 6: 1 has not been observed. The increase of β‑hydroxybutyrate levels in blood of mice fed with both KDs has been noticed. CONCLUSIONS: In conclusion, results of evaluation of the number of Enterococcus faecalis and Escherichia coli may suggest that a KD high in animal fat affects the gut microbiota composition in 129SV mice