War has been declared against Staphylococcus aureus

It has been established since the mid-1970s that the skin of individuals suffering from atopic dermatitis is generally colonized by Staphylococcus aureus. Highly pathogenic, its name often refers to tricky infections⁴¹. It is in particular responsible for the largest number of nosocomial infections (in hospitals), as well as skin or foodborne infections of variable severity. It was also recently discovered that the infection is more severe where these bacteria are present in greater numbers and belong to certain specific strains⁴². Meanwhile, technical progress made in the field of genetics has allowed the composition of the cutaneous flora of affected individuals to be better described, and has revealed a reduced bacterial diversity⁴³. But up until now, it was not known whether the abundance of Staphylococcus aureus was the cause of atopic dermatitis or an observed consequence of the dysbiosis of the cutaneous microbiota.

Staphylococcus aureus, herald of the disease

A recent prospective clinical trial has just shown that colonization by Staphylococcus aureus precedes the onset of the disease in children⁴⁴. This led to imparting a causal role to the bacterium in the onset of the disease, which partly contradicts the conclusion of another recent study⁴⁵ (which however also incriminates Staphylococcus strains). It required two years of study to arrive at this conclusion: the researchers regularly analyzed skin samples taken from the elbow creases and the axillae, areas that are classically affected. First result: one child in four developed atopic dermatitis. Secondly: the proportion of Staphylococcus aureus increases markedly from the age of three months in infants who were subsequently reported to have atopic dermatitis. On the contrary, other bacteria, less abundant in infants suffering from atopic dermatitis, seem to have a potentially protective role⁴⁶.

Other methods of eradication

Non-clinical and in vitro experiments have shown that Staphylococcus aureus could promote the disease in individuals with a genetic predisposition by triggering toxic and/or inflammatory reactions in skin cells exposed directly to the microbes⁴⁷. By extrapolation, researchers thought that elimination of this bacterium could be beneficial in the treatment of atopic dermatitis. Relatively effective treatments already exist–topical antimicrobials, antibiotics, dilute bleach baths–but paradoxically, it is not known whether they really eliminate Staphylococcus aureus colonization nor what is their impact on the cutaneous microbiota. For this reason, similar to transplants of fecal flora, transplants of cutaneous microbiota⁴⁸ containing bacteria known to act against Staphylococcus aureus is an emerging protocol. The first trials conducted on affected individuals led to a considerable reduction in colonization by Staphylococcus aureus. We wager that the next trials will validate this promising start and will be accompanied by improvements in treatment.