Researchers at the Wellcome Sanger Institute have mapped the genetic code of the oldest publicly-available strain of cholera. The bacterium came from a British soldier from World War One (WWI).
The sixth pandemic
Cholera is an infection of the small intestine by some strains of the V. cholerae bacterium caused by ingesting contaminated food or water. The disease can lead to epidemics or even global pandemics.
During WWI a historical global cholera pandemic, known as the sixth pandemic, occurred. It was during this period that the now mapped strain was collected and stored.
In 1916, a strain was extracted from the stool of a British soldier. The bacterium was then deposited in the National Collection of Type Cultures (NCTC)* in 1920.
The oldest publicly-available V. cholerae
It is believed to be the oldest publicly-available V. cholerae. In order to map its genetic code, researchers at the Sanger Institute revived the WWI soldier's bacteria.
"We have decoded the genome of what we believe to be the oldest archived 'live' sample of V. cholerae. It is a privilege to be able to look at the genome of this isolate. Studying strains from different points in time can give deep insights into the evolution of this species of bacteria and link that to historical reports of human disease," said Professor Nick Thomson, lead author from the Wellcome Sanger Institute.
The team, however, found the soldier's strain of V. cholerae was not the type capable of causing an epidemic cholera. It was therefore unrelated to the V. cholerae responsible for the sixth pandemic.
"Even though this isolate did not cause an outbreak it is important to study those that do not cause disease as well as those that do. Hence this isolate represents a significant piece of the history of cholera, a disease that remains as important today as it was in past centuries," explained Thomson.
Researchers also found that the sequenced strain possessed a gene for ampicillin resistance. This is crucial as it provides evidence that antibiotic resistance in bacteria existed before the introduction of antibiotics.
"The National Collection of Type Cultures grows and maintains over 5,000 strains of bacteria from the last hundred years or so. Studying these bacteria offers a window into the past and helps scientists to understand how bacteria evolve over time, and the roles they played in history," said Julie Russell, Head of Culture Collections at NCTC.
The study is published in Proceedings of the Royal Society B.