Antibiotic resistance: a surprising timeline

Scientists from the Institut Pasteur have retrospectively identified early cases of Salmonella resistance to ampicillin, a broad-spectrum antibiotic that is still widely used today. By analyzing the genomes of hundreds of historical samples of Salmonella, they proved that resistance first emerged well before ampicillin was released on the market for human use. Their discovery suggests that low doses of penicillin G, routinely fed to livestock in North America and Europe in the 1950s to boost growth, may have encouraged bacteria resistant to this new antibiotic to evolve and spread to humans just a few years later. The findings have been published in the journal The Lancet Infectious Diseases.

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