Science: Research opens windows for Listeria antibiotic treatment

Listeriosis, or infection with the foodborne pathogen Listeria, affects nearly 1,600 people each year in the U.S. alone. Most cases pass after a few days either without treatment or with an antibiotic like ampicillin. However, a recent discovery may have opened up a powerful antibiotic as a treatment option, possibly changing the way we handle Listeria infections.

Researchers from the University of Edinburgh have found that the bacteria Listeria responds to an antibiotic called fosfomycin, which flies in the face of previous understanding of the bacteria — that it carried genes that made it resistant.

Early laboratory tests from the Scottish team suggested that fosfomycin was ineffective against Listeria because the pathogen could easily break down the drug, thanks to its genes. Newer tests show how the drug can be effective, however — and it has to do with genes that the researchers weren’t seeing before.

Later tests showed how fosfomycin was, in fact, able to kill Listeria in infected cells and infected mice, despite the drug-destroying gene. How? It turns out some genes only activate when the bacteria infect the body, and those genes cancel out the gene-destroying one.

This process is an example of epistasis, or the interaction of genes, usually the suppression of one by another. This is why the early laboratory tests showed different results — the epistatic process wasn’t observed because infection of a cell or mouse didn’t occur in the earlier tests.

The researchers say the antibiotic might be suitable as a treatment in severe listeriosis cases.

“Our study focused on Listeria, but this important discover may be relevant for other species of bacteria too,” said Jose Vazquez-Boland, research lead. “It is encouraging that we may be able to repurpose existing drugs in the race against antibiotic resistance.”

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