Bacteria linked to global cholera pandemic found in 200-year-old intestine

Researchers, who worked with a nearly 200-year-old sample of preserved intestine, have traced the bacterium behind a global cholera pandemic that killed millions.

A version of the same bug still continues to strike vulnerable populations in the world's poorest regions.

Using sophisticated techniques, the team at McMaster University and the University of Sydney has mapped the entire genome of the elusive 19th century bacterium.

The findings are significant because, until now, researchers had not identified the early strains of cholera, a water-borne pathogen.

The discovery significantly improves understanding of the pathogen's origin and creates hope for better treatment and possible prevention.

Researchers have now confirmed the first of two types of cholera, known as classical, was likely responsible for five of the seven devastating outbreaks in the 1800s, all of which most likely originated in waters of the Bay of Bengal.

That strain of cholera had remained a mystery because researchers were unable to examine samples from early victims.

The pathogen thrives in the intestines, never reaching teeth or bones, so remnants of its DNA do not exist in skeletal remains.

Despite many known cholera burials, access to historical cholera DNA had seemed impossible since it can only be found in soft-tissue remains.

But graduate student Alison Devault and evolutionary geneticists Hendrik Poinar, Brian Golding and Eddie Holmes-working with a team of other scientists-learned that a remarkable collection of tissue specimens was housed at a medical history museum. The Mutter Museum was established by the College of Physicians of Philadelphia in 1858, after the city itself was devastated by cholera earlier in the century.

Researchers carefully sampled a preserved intestine from a male victim of the 1849 pandemic and extracted information from tiny DNA fragments to reconstruct the Vibrio cholera genome.

The results could lead to a better understanding of cholera and its modern-day strain known as El Tor, which replaced the classical strain in the 1960s for unknown reasons and is responsible for recent epidemics, including the devastating post-earthquake outbreak in Haiti.

The research is published in The New England Journal of Medicine.