Whole genome analysis of two multiresistant Escherichia coli strains, effect of grape polyphenols on bacterial growth

Abstract

Bacterial resistance to antibiotics has increased alarmingly over the last few decades. On the contrary, the benefits of natural products of vegetable origin have been used in empirical treatments of infections for centuries without generating bacterial resistance. The aim of this work was to study the resistome of two multidrug resistant Escherichia coli strains isolated from the natural intestinal microbiota of healthy animals, and the effect of a red grape polyphenol extract on their growth.Whole genome analysis of both E. coli strains C6898 and C6840 was performed in an Illumina HiSeq 1500 sequencing system and chromosome and plasmid reconstruction were performed with PLACNETw web-based tool. Antimicrobial susceptibilities of the E. coli strains were tested. In vitro synergistic effects of a polyphenol extract from skins of Graciano red grapes in combination ampicillin were studied by the checkerboard method. The genomes of both strains were reconstructed.Strain C6898 showed 60 different genes related to antibiotic resistance, which were located in its chromosome and in two of its three additional plasmids. Strain C6840 showed 59 antibiotic resistance related genes located in its chromosome and in its single-plasmid. Both E. coli strains showed high resistance to ampicillin. The grape polyphenol extract showed an inhibitory effect on bacterial growth of both strains and synergistic activity (FIC= 0.4-0.6) in combination with the antibiotic ampicillin. In the presence of 1.5 – 3.1 mg/mL of the polyphenol extract, both resistant strains became sensitive to ampicillin and their growth was totally inhibited. Epicatechin and malvidin were also assayed against strain C6840 and both polyphenols showed bacterial growth inhibition. A concentration of 1.33 mg/mL malvidin showed bactericide effect.This study shows that grape polyphenol extracts could contribute to reduce the current prophylactic and therapeutic use of antibiotics, and thus contribute to combat widespread antibiotic resistance.