Antibiotics Cause Long-Lasting Effects on the Skin’s Microbiomes

RESIDENT bacterial communities of the skin, including those that compete with diseases like Staphylococcus aureus, can be greatly reduced following the application of topical antibiotics, suggests a new study performed by the Grice Lab, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA. “We know antibiotics and antiseptics can be effective in stopping the growth of certain bacteria, but we wanted to know about the larger impact these treatments can have on the resident microbial communities on the skin,” said lead author Dr Adam SanMiguel, Grice Lab, Perelman School of Medicine, University of Pennsylvania.

The first branch of the study was conducted by applying a range of antibiotics, including a narrowly targeted mupirocin ointment and a broadly applicable triple-antibiotic ointment, to the skin of hairless mice. As expected, the researchers observed alterations in the microbial communities of the mice’s skin, but, more importantly, they noted the duration of that alteration, which was for days after treatment. “That disruption opens the door for colonisation by an unwanted strain,” noted Dr SanMiguel.

In a parallel study, the effect of antiseptics was also investigated. Hairless mice were treated with alcohol or povidone-iodine and then compared to two control groups. These results proved surprising: neither antiseptic caused such a noticeable change in the mice’s biomes to allow them to be grouped meaningfully, nor were there any significant differences between the treated group and controls with regards the relative number of individual bacterial strains. “We thought antiseptics would be even more disruptive to microbial communities than antibiotics since they are less targeted, but it turns out the opposite is true,” commented Dr SanMiguel.

Further research is required to validate these findings, but researchers are confident that this research will form a foundation from which to study the ways the skin defends against infection. “This gives us a better understanding of how topical antimicrobials affect the skin microbiome and what kind of impact their disturbance can have in the context of pathogenic colonisation. This helps us anticipate their potential effects,” concluded senior author Prof Elizabeth Grice, University of Pennsylvania. Testing in humans is already underway.

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