A study undertaken by scientists at the University of California, San Diego (UCSD) and published in The Journal of Experimental Medicine indicates that the pigment responsible for the characteristic golden colour of Staphylococcus aureus is a virulence factor that enables S. aureus to neutralize neutrophil host-defence mechanisms.

S. aureus can be a deadly human pathogen; it flourishes in hospitals, causing infections of the bloodstream and surgical wounds. The emergence of antibiotic-resistant strains, known as methicillin-resistant S. aureus (MRSA), is a major threat to public health and means that alternative treatment strategies are being sought.

S. aureus produces carotenoids, which give it its characteristic golden colour. These molecules are similar to those that make carrots orange, which are known to have anti-oxidant properties. The authors showed that a mutant strain of S. aureus that could not produce carotenoids was more susceptible to being killed by reactive-oxygen species produced by neutrophils than was wild-type S. aureus, and this mutant did not form abscesses when injected into the skin of mice.

The senior author of the paper, Victor Nizet, said that the study “provides a novel target for treatment of serious Staph infections” (UCSD News). He suggests that “a treatment strategy to inhibit the Staph pigment would disarm the pathogen, making it susceptible to clearance by our normal immune defenses.” (UCSD News). However, Mark Enright, from the University of Bath (UK), said that, although the research raised hope for developing new ways to combat S. aureus, “Staph has a large number of virulence factors and toxins and to target just one of these may prove inadequate.” (BBC News).