Staph aureus opens the door to skin infection by other viruses

If you have eczema, I'm sure you never thought it was a good thing that your skin was colonized by Staphylococcus aureus, the cause of so many runaway infections. If that weren't bad enough, scientists have now shown that S. aureus produces a toxin that enables other viruses to more easily infect skin cells.

The work, done by a group led by Donald Leung at National Jewish Health Center in Denver, was presented this week at the annual meeting of the American Academy of Allergy, Asthma, and Immunology in Orlando, Florida.

S. aureus produces a number of toxic substances, but one stands out in particular: "alpha-toxin." The researchers pretreated normal human skin cells with a variety of toxins, and then incubated the cells with two viruses: vaccinia and herpes simplex. Only alpha-toxin increased the amount of virus infecting the cells, compared to a control experiment. Alpha-toxin increased viral load of herpes in the skin cells by threefold, and that of vaccinia tenfold.

This may explain, the authors say, why patients with eczema are much more susceptible in general to viral skin infections than "normal" people. Eczema patients, for whatever reason, host a semi-permanent population of S. aureus, which is pumping out alpha-toxin and opening the door for its viral relatives.

[added later] It's well-known that people with eczema are more likely to develop warts, which are caused by viruses. Maybe if there were a way to neutralize S. aureus alpha-toxin, we could cut down on the number of times we get viral skin outbreaks and warts too.