Does leishmania infection affect the skin microbiome?

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Researchers from the University of Pennsylvania (PA, USA) have demonstrated that leishmania infection alters the skin microbiome in both humans and mice, and that microbial composition can in turn affect disease severity. In addition, they reported that naïve mice can acquire the altered microbiota when kept in close contact with infected mice.

It has previously been reported that the skin microbiome can play an important role in processes such as allergies, inflammation and wound healing. This study, published recently in Cell Host & Microbe, therefore aimed to investigate whether the microbiota might influence the outcomes in leishmaniasis – a disease which results in sores on the skin.

The team examined swabs taken from 44 human leishmaniasis patients, discovering a pattern of dysbiosis. The researchers compared swabs taken from skin lesions with those taken from unaffected areas of skin, observing that lesion samples contained reduced bacterial diversity.

To investigate this further, the group used a mouse model of infection, discovering that leishmania infection induced a change in the skin microbiota. They also observed an association between microbial diversity and disease severity – Staphylococcus dominated in mice that resolved infections whereas Streptococcus was dominant in lesions on mice with persistent infection.

It was also observed that this microbial dysbiosis could be acquired by naïve mice when housed with infected animals, a core finding of the study. The team discovered that mice with acquired dysbiosis displayed a heightened inflammatory response and suffered more severe disease when subsequently infected with leishmania.

Author Phillip Scott (University of Pennsylvania) commented: “The transmission of dysbiosis in the skin from one animal to another is a key finding and the fact that we saw similar patterns of dysbiosis in humans suggests there could be some very practical implications of our work when it comes to treating people with leishmaniasis.”

Previous studies have reported mixed results regarding the effectiveness of antibiotics in treating leishmaniasis. The team stated that these additional findings about the alteration of the microbiome may cause individuals to rethink the role of antimicrobials in treatment.

Moving forwards, the team are hoping to examine whether sharing of a microbial dysbiosis occurs in other infections in addition to investigating the effect of the skin microbiome on other process, such as wound healing.

Co-senior author Elizabeth Grice (University of Pennsylvania) concluded: “To my knowledge, this is the first case where anyone has shown that a pre-existing skin microbiome can influence the outcome of an infection or a disease. This opens the door to many other avenues of research.”

Sources: Gimblet C, Meisel JS, Loesche MA et al. Cutaneous Leishmaniasis Induces a Transmissible Dysbiotic Skin Microbiota that Promotes Skin Inflammation, Cell Host Microb. doi:10.1016/j.chom.2017.06.006 (2017) (Epub ahead of print); https://news.upenn.edu/news/perturbed-skin-microbiome-can-be-contagious-and-promote-inflammation-penn-study-finds

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