Influence of the Type of Diet on the Incidence of Pathogenic Factors and Antibiotic Resistance in Enterococci Isolated from Faeces in Mice

Abstract

A comparative study on potential risks was carried out in a collection of 50 enterococci isolated from faeces of mice fed a standard or a high-fat diet enriched with extra virgin olive oil, refined olive oil or butter, at the beginning, after six weeks and after twelve weeks of experiments. Strains were biochemically assessed and genetically characterized. E. faecalis and E. casseliflavus were the most frequently isolated species in any diet and time points. Apart from the fact of not having isolated any strain from the virgin olive oil group during the last balance, we found statistically significant differences p < 0 . 05 among the diets in the percentage of antibiotic resistance and in the presence of the enterococcal surface protein gene (esp), as well as a tendency p < 0 . 1 for the presence of the tyrosine decarboxylase gene (tdc) to increase over time in the group of isolates from the standard diet. When the resistance of the strains to virgin or refined olive oil was studied, only the group of enterococci from high fat diets showed a significantly higher percentage of resistance to refined olive oil p < 0 . 05 , while both types of oil equally inhibited those isolated from the standard diet p > 0 . 05 .

Prevalence of an Intestinal ST40 Enterococcus faecalis over Other E. faecalis Strains in the Gut Environment of Mice Fed Different High Fat Diets

“…Consequently, in another subsequent study, the safety level of enterococcal strains isolated from the intestinal microbiota of mice fed a standard diet or one enriched with butter and virgin and refined olive oil was addressed, by assessing the resistance of the strains to antibiotics, virulence factors and the production of biogenic amines, in order to ultimately determine if there are statistically significant differences among four groups of enterococci isolated from those four different diets. Thus, as also reported in [14], we found statistically significant differences among the diets in the percentage of antibiotic resistance and in the presence of the enterococcal surface protein gene (esp). When the resistance of the strains to virgin or refined olive oil was studied, only the group of enterococci from the mice fed the high fat diets showed a significantly higher percentage of resistance to refined olive oil, while both types of oil equally inhibited those isolated from mice under the standard diet [14].…”

“…Thus, as also reported in [14], we found statistically significant differences among the diets in the percentage of antibiotic resistance and in the presence of the enterococcal surface protein gene (esp). When the resistance of the strains to virgin or refined olive oil was studied, only the group of enterococci from the mice fed the high fat diets showed a significantly higher percentage of resistance to refined olive oil, while both types of oil equally inhibited those isolated from mice under the standard diet [14]. Additionally, we had also been unable to isolate any strain from EVOO-fed mice at the end of the experimental period.…”

“…A large collection of enterococci isolated from faeces of mice fed with different high fat diets enriched in butter, virgin olive oil and refined olive oil and from mice fed with standard chow [8,11] was screened for E. faecalis strains, and fifteen of them were uncovered [14] and further studied in the present report. The objective of this work is to provide basic knowledge on how different strains of the same intestinal species can thrive and be selected in a controlled population and if a specific diet may have an influence on certain strains or traits.…”

“…These strains had been subjected to Randomly Amplified Polymorphic DNA (RAPD) analysis to ensure they were genetically different [14]. However, when undergoing MLST analysis as shown above, all of them belonged to only three sequence types: ST9, ST40 and ST150 (one strain).…”

“…All the E. faecalis strains detected in a wider enterococci collection [14] were selected for this study, numbering, in total, fifteen strains. The enterococci collection had been isolated from mice fed on different diets.…”