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It's thought to be the first study to demonstrate that the skin's microbiome can help determine whether or not you'll catch an infection and could soon lead to the development of a preventative probiotic.

The research team observed the skin microbiome of eight participants before, during and after infecting them with the bacteria Haemophilus ducreyi on the arm.

This bacteria is not only known to cause chancroid, it's also known to provoke the onset of skin ulcers in children living in central Africa and the South Pacific.

Reactions to the bacteria differ from person to person: Some clear the infection straight away, while others develop abscesses, according to the researchers.

They compared the skin microbiome of participants who cleared the infection to those who developed pustules that would later become abscesses.

Skin microbiomes of individuals demonstrating one reaction or the other were vastly different even before they became infected, say the researchers.

The bacterial colonies of the skin microbiome change their composition in response to the infection, whether the individual resolves it quickly, or whether it progresses, according to the study.

"The number one question is whether the microbiome that is present in patients who resolve the infection is merely a signature of an innate immune system that is good at clearing the skin of infections or are there specific bacteria in that composition that are helping the immune system clear the pathogen," says lead author Dr. Stanley Spinola of the Indiana University School of Medicine.

The paper on the project was published in the journal mBio, an open access journal of the American Society for Microbiology.

Symptoms of chancroid appear within four to 10 days after exposure by sexual contact, according to the New South Wales government health watchdog.

They include ulcers or sores, marked by soft, irregular borders that bleed easily upon contact, in the genital area including the anus.