Differential effects of oligosaccharides on the effectiveness of ampicillin against Escherichia coli in vitro

Abstract Background The mounting antibiotic resistance emphasizes an urgent need for alternatives. Recent investigations indicate that non-digestible oligosaccharides (NDOs), besides their prebiotic properties, can directly interact with pathogenic bacteria. In this study, the protective effect of alginate-oligosaccharides (AOS), chitosan-oligosaccharides (COS), galacto-oligosaccharides (GOS) and fructo-oligosaccharides, against enteropathogenicEscherichia. coli was investigated. Methods The effect of these NDOs onE. coli growth, adhesion and E. coli-induced inflammatory response (IL-8 release) of HT-29 intestinal epithelial cells were determined in vitro in the presence or absence of ampicillin, using minimum inhibitory concentration (MIC) assay, anti-adhesion assay and ELISA, respectively. Results At low concentrations 0.5% and 1%, AOS decreased theE. coli growth, while high GOS concentrations (6%, 8%, 10%) were effective. Interestingly, the combination of the low concentrations of AOS with ampicillin (2 µg/mL) exerted a 2-fold decrease in the MIC level of ampicillin against E. coli. AOS also concentration dependently reduced the adherence of E. coli to HT-29 cells. The combination of AOS with ampicillin further increased these anti-adhesive properties. Pre-incubation of HT-29 cells with AOS, COS or GOS significantly hampered the E. coli-induced IL-8 release. Conclusion Current study highlights the direct effects of NDOs onE. coli growth, adhesion and inflammatory responses of HT-29 cells in vitro.