How S. aureus bacteria are trying to get under your skin

“Does it tickle, or does it itch?” Dr Knock’s famous question in Jules Romains’ play of the same name may have inspired the authors of a recent study. Their aim? To better understand the mechanisms that trigger itching (sidenote: Itch Itch is an unpleasant sensation that evokes a desire to scratch. Itch originates in the nerve endings just beneath the skin, at dedicated receptors called pruriceptors. It then follows nerve pathways up to the brain, where it activates sensory (feeling the itch), emotional (wanting to scratch), and motor (actually scratching) brain areas.  
Source : Ameli ) and the resulting irresistible urge to scratch. They achieved their results thanks to a series of experiments on mice and samples of human nerves and skin.

From bacteria to scratching...

The focus of their research: the Staphylococcus aureus bacterium, widely present on our skin. Staphylococcus aureus feeds on the skin lesions of those prone to atopic dermatitis and plays a role in impetigo, a contagious skin disease feared in nurseries and kindergartens. To its resume can be added a direct involvement in pruritus, the scientific name for itching.

Its modus operandi has now been revealed: S. aureus produces a protein called V8, which binds to the skin receptor responsible for itching. By activating this receptor, V8 triggers an alert that travels via a nerve pathway to the brain. The response to the itch is immediate: scratching, often frantic, to the point of damaging the skin.

... then to invasion or spread

Isn’t that exactly what the bacterium wanted? While not wanting to impart to a microorganism any sinister intentions, all of this clearly suits Staphylococcus aureus: scratching is the perfect way for it to reach new tissue, such as the hand or paw used to relieve the itch, or even new individuals, if they happen to be close enough to the skin being scratched. Better still, the lesion induced by scratching is a chance for the bacteria to penetrate a little deeper into the skin. In short, whether through spread or invasion, S. aureus has everything to gain by making us scratch.