The effect of 20-hydroxyecdysone on the susceptibility of Escherichia coli to different antibiotics.

Aims: The aim of this study was to investigate the influence of 20-hydroxyecdysone (20E) on the susceptibility of growing Escherichia coli to antibiotics.

Methods And Results: Susceptibility of E. coli to antibiotics in the presence of 20E was estimated by determination of the colony-forming ability and the specific growth rate. Pretreatment with 20E decreased the bactericidal effect of ciprofloxacin (0·3 and 3·0 μg ml ), streptomycin (10 and 40 μg ml ) and kanamycin (10 μg ml ) and increased the bactericidal action of 0·03 μg ml ciprofloxacin. To study the influence of 20E on gene expression, we used strains of E. coli carrying fusions of promoters of relevant genes with the structural gene of β-galactosidase. 20E had no marked effect on the expression of antioxidant genes katG, katE, sodA and the rpoS gene (general stress response), while it (alone or combined with ciprofloxacin) markedly stimulated expression of the sulA gene belonging to the SOS regulon (DNA damage response).

Conclusion: In growing E. coli, 20E modulated the bactericidal action of antibiotics and stimulated the SOS response.

Significance And Impact Of The Study: The results of this study may be used to enhance the efficiency of antibacterial therapies.