SOKOTO STATE — Researchers led by the Liverpool School of Tropical Medicine have identified a previously undescribed species of Treponema bacteria in mouth microbiome samples taken from children with noma in Nigeria. The study, published in PLOS Neglected Tropical Diseases, analyzed samples from 19 children and involved researchers from the University of Liverpool, Médecins Sans Frontières and the Noma children's hospital in Sokoto, Nigeria.

Noma begins as a sore on the gums and then destroys the tissues of the mouth and face. The disease mainly affects young, poor and malnourished children, with most cases reported in the Sahel region of Africa. Without treatment, it is fatal in 90% of cases. The precise underlying cause has never been established.

If noma reaches its necrotising stage without treatment, it results in death. Patients treated swiftly with antibiotics at that stage usually recover, but with extensive disfigurement and lifelong stigma and social exclusion.

Genetic analysis of the samples revealed lower levels of normal bacteria and increased levels of other bacterial strains in the mouth microbiome of noma patients. Deeper analysis uncovered the previously undescribed Treponema species, currently called Treponema A, in most of the patient samples. The bacterium was identified by Angus O'Ferrall, a PhD student on the team. Researchers reanalysed older samples from other noma patients and found Treponema A was also present.

"It was a great reveal," said Adam Roberts, a senior author on the study. "I was astonished." He cautioned that the finding does not establish what role the bacterium plays in the disease. "We don't know causality," he said. "We don't know if it can colonise a noma wound, because of the architecture and the environment, or if it causes the noma wound."

Current diagnosis relies on visible symptoms. "At the moment, the only thing that we have is a clinical diagnosis based on symptoms. And that can be a foul smell or holes in the skin and the tissues," he said. "But if we know that actually Treponema A, for example, is always or 99% associated with the development of noma at the gingivitis stage then we could detect and treat prophylactically with antibiotics to stop it progressing."

Using broad-spectrum antibiotics to treat noma risks increasing antimicrobial resistance, Roberts said, and a targeted treatment aimed at a specific bacterium could reduce that threat. He added that the reduced levels of healthy bacteria in noma patients suggest a potential preventive intervention with probiotics. The team is conducting a larger study using samples from more noma patients and healthy individuals in the same communities across multiple countries.

"A different version of this Treponema bacteria causes syphilis, which is known for being a sexually transmitted infection, but can and does also cause wounds and ulcers within the mouth," said Michael Head, a senior research fellow in global health at the University of Southampton. "The study is a valuable starting point and should help stimulate greater interest from both the research community and funders," said Philippe Guérin, director of the Infectious Diseases Data Observatory.