Inhibition of virulence of Staphylococcus aureus – a food borne pathogen – by squalene, a functional lipid

Increased resistance of Staphylococcus aureus – a pathogen responsible for hospital and food
related infections – to several antibiotics has become a major concern. Staphyloxanthin, a
carotenoid, is attributed to be the major virulent factor contributing to the pathogenicity
of S. aureus. The present study investigated squalene for its ability to render S. aureus avirulent
and consequent effect on staphyloxanthin. Squalene inhibited staphyloxanthin synthesis
in S. aureus as confirmed by spectral profiling and HPLC analysis. It also reduced the haemolytic
ability of the pathogen in a dose dependent manner (0.05–0.75 mM). Squalene pretreatment
increased the susceptibility of the pathogen to oxidants by 48% and reduced the
neutrophil resistance by about 82%. Further, biofilm forming ability of S. aureus was also affected
by squalene.This is the first evidence of the antivirulent effects of squalene, a functional
lipid, and, provides an alternate approach for treating S. aureus infections.