The unnamed 72-year-old woman visited a local clinic six days after she cut open her left calf on a tree branch, according to a case study in BMJ Case Reports. The woman was hiking on a laval field when she lost her footing and impaled her leg on a branch close to the ground, the report said. She was given stitches and sent home with a five-day course of antibiotics.

After she finished the antibiotics, she visited an emergency department in Washington state, as she was worried by discolored skin and foul-smelling liquid oozing from the wound.

When doctors inspected her wound, they found signs the soft tissue was infected and the skin was dying away. The doctors ran tests including scans which prompted concern she had a necrotising soft tissue infection (NSTI), which is where the tissue dies away.

Conditions which cause tissue to die are sometimes referred to as “flesh-eating” because it makes the skin die as if it has been devoured.

The woman was prescribed another round of antibiotics, and she had surgery to cut the infection out of her leg. Samples taken from her wound and deep tissue came back positive for the bacteria Leclercia adecarboxylata (L. adecarboxylata). After six days in hospital, she was discharged with antibiotics. The woman had pressure wound therapy, in which fluid is removed to help an area heal, and later a skin graft.

L. adecarboxylata is found among the gut bacteria of animals and humans, but it is rare for humans who do not have weak immune system to be infected with it, members of the team who treated the woman wrote in the BMJ report. But recent case reports suggest the bacteria can cause a wide range of infections in those who have weak immune systems, and can even cause death.

This is thought to be the first case of L. adecarboxylata causing an NSTI in a person with a working immune system, the authors said. Acknowledging the potential limitations of their case report, the authors said they may have classified the bacteria as L. adecarboxylata in error, as it has similar characteristics to Escherichia coli (E.coli) when plated in a lab.

Although it is unlikely for L. adecarboxylata to cause an infection in a person with a working immune system, doctors should keep the possibility in the back of their minds when treating patients, the authors said.

“Fortunately,” the authors said L. adecarboxylata seems to be responsive to a number of common antibiotics.