Innate Immune Response against Staphylococcus aureus Preincubated with Subinhibitory Concentration of trans-Anethole

Abstract

The study aimed to analyze morphological and functional changes of <i>Staphylococcus aureus</i> cells due to <i>trans</i>-anethole (a terpenoid and the major constituent of fennel, anise, or star anise essential oils) exposition, and their consequences for human neutrophils phagocytic activity as well as IL-8 production (recognized as the major chemoattractant). The investigation included the evaluation of changes occurring in <i>S. aureus</i> cultures, i.e., staphyloxanthin production, antioxidant activities, cell size distribution, and cells composition as a result of incubation with <i>trans</i>-anethole. It was found that the presence of <i>trans</i>-anethole in the culture medium reduced the level of staphyloxanthin production, as well as decreased antioxidant activities. Furthermore, <i>trans</i>-anethole-treated cells were characterized by larger size and a tendency to diffuse in comparison to the non-treated cells. Several cell components, such as phospholipids and peptidoglycan, were found remarkably elevated in the cultures treated with <i>trans</i>-anethole. As a result of the aforementioned cellular changes, the bacteria were phagocytized by neutrophils more efficiently (ingestion and parameters associated with killing activity were at a higher level as compared to the control system). Additionally, IL-8 production was at a higher level for <i>trans</i>-anethole modified bacteria. Our results suggest that <i>trans</i>-anethole represents a promising measure in combating severe staphylococcal infections, which has an important translational potential for clinical applications.