Staphylococcus aureus. The name means, literally, “golden grape clusters.” Upon staining, these round bacteria are visualized in clumps that resemble bunches of grapes. Every microbiology student is familiar with the most notorious member of the Staphylococcus species, S. aureus, which often produces a distinct yellow pigment when grown on agar plates containing blood. This bacterium itself causes a wide range of illnesses, ranging from food poisoning to deadly skin infections. Of great concern is the fact that strains that resist a number of antibiotics–including methicillin–have been increasingly isolated no only in hospital settings, but also in the community. Vancomycin-resistant strains have also been isolated, but are not yet widespread. It was recognized almost 25 years ago that the S. aureus yellow pigment consists of a number of carotenoids, similar to those produced in carrots and other fruits and vegetables. Studies of these carotenoid pigments have revealed their free-radical scavenging properties, protecting cells and tissues from the damaging effects of free radicals and singlet oxygen. (In other words, they’re antioxidants). Interestingly, one mechanism by which phagocytic cells of the host immune system destroy pathogenic invaders is via release of reactive oxygen species. Do these bacterial carotenoids protect S. aureus against damage initiated by the host immune system?
(Continued at Aetiology)