Extract of Pelargonium sidoides (EPs^® 7630) inhibits the interactions of group A-streptococci and host epithelia in vitro

Abstract 

EPs^® 7630 is an extract of the root of the South African geranium Pelargonium sidoides. Clinical data have shown that this herbal drug preparation can be used to treat upper respiratory tract infections (URTI). The objective of this study was to investigate the impact of EPs^® 7630 on group A-streptococci (GAS) adhering to and invading host epithelial cells in vitro.

Adhesion was assessed by a flow cytometric adhesion assay using calcein-AM-stained S. pyogenes (DSM 2071) as test organism, and HEp-2 cells and buccal epithelial cells (BEC) as substrata. For cell invasion, HEp-2 cell monolayers were infected with S. pyogenes. Intracellular bacteria were determined using a penicillin/gentamicin-protection assay. EPs^® 7630 was applied in therapeutically relevant concentrations between 0 and 30μg/ml in both test systems.

Compared to controls, EPs^® 7630 significantly reduced GAS adhesion to HEp-2 cells in a concentration-dependent manner by up to 46% (p<0.001). This was semi-quantitatively confirmed by fluorescence microscopy. Adhesion kinetics additionally indicated a specific antagonistic effect on GAS adhesion. Pre-treatment of epithelial cells or GAS with EPs^® 7630 showed that it targets GAS rather than HEp-2 cells. However when using BEC as substrata, GAS adhesion increased 7-fold under the influence of EPs^® 7630 (p<0.001). In viability assays, HEp-2 suspension contained over 90% vital cells, whereas only 10% of the BEC were viable. EPs^® 7630 reduced GAS invasion of HEp-2 cells significantly when the data taken at time points 60, 120, and 180min () were analyzed.

In conclusion, EPs^® 7630 develops complementary anti-infective properties: Firstly, EPs^® 7630 reduces bacterial adhesion to intact epithelial cells and thus protects the organism from bacterial colonization and infection/super-infection. Secondly, EPs^® 7630 enhances the attachment of bacteria to decaying BEC. In this way pathogens may be trapped and rendered inactive. Thirdly, the inhibition of GAS invasion of epithelial cells protects the host from microorganisms that may have evaded host defences and antibiotic treatment, and therefore prevents recurrent infections. Thus, our investigations provide a rational basis for the treatment of URTI with EPs^® 7630.

Keywords: Pelargonium sidoides, EPs^® 7630, Group A-streptococci (GAS), Adhesion, Invasion, Upper respiratory tract infections (URTI)