Genetic code of WWI soldier's cholera mapped

The bacterium was isolated from a British soldier and stored for over 100 years before being revived and sequenced

Genetic code of WWI soldier's cholera mapped

British Expeditionary Force on the Western Front, 1914-1915. Image credit: Imperial War Museums (Wikimedia Commons) Imperial War Museums (Wikimedia Commons)
The British Expeditionary Force on the Western Front. An 18-pounder field gun and crew on the Armentieres sector of the front line, 7 December 1914.

The oldest publicly-available strain of the cholera-causing bacterial species, Vibrio cholerae, has had its genetic code read for the first time by researchers at the Wellcome Sanger Institute and their collaborators. The bacterium was isolated from a British soldier during World War One (WWI) and stored for over 100 years before being revived and sequenced.

The results, published today (10 April) in Proceedings of the Royal Society B, show that this strain is a unique, non-toxigenic strain of V. cholerae that is distantly related to the strains of bacteria causing cholera pandemics today and in the past.

Vibrio cholerae (V. cholerae) bacteria. If swallowed, these highly contagious organisms release toxins in the gut that cause severe diarrhoeal disease. Image Credit: Dave Goulding, Wellcome Sanger InstituteDave Goulding, Wellcome Sanger Institute
Vibrio cholerae (V. cholerae) bacteria. If swallowed, these highly contagious organisms release toxins in the gut that cause severe diarrhoeal disease.

Cholera is a severe diarrhoeal disease caused by ingesting food or water that is contaminated with toxigenic V. cholerae. The disease can spread rapidly in epidemics and in global pandemics.

WWI coincided with an historical global cholera pandemic, known as the sixth pandemic, which was caused by ‘classical’ V. cholerae. Surprisingly, very few soldiers in the British Expeditionary Forces contracted cholera during the war, despite the disease being considered as a threat.

In 1916, a strain of V. cholerae was extracted from the stool of a British soldier who was convalescing in Egypt. Reports indicate that the isolate was taken from ‘choleraic diarrhoea’. The bacterium was stored and subsequently deposited in the National Collection of Type Cultures (NCTC)* in 1920.

Researchers at the Sanger Institute revived the WWI soldier’s bacteria – thought to be the oldest publicly-available V. cholerae sample – and sequenced its entire genome.

The team found this particular strain of V. cholerae was not the type capable of causing epidemic cholera, and was unrelated to the classical V. cholerae that caused the sixth pandemic at the time of WWI.

“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. 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.”

Professor Nick Thomson, lead author from the Wellcome Sanger Institute

“Reports in the literature indicated that there was something unusual about the strain of bacteria from the WWI soldier. It’s promising to see that our genomic information aligns with those historical records. We also made other observations – under the microscope, the bacterium looks broken; it lacks a flagellum – a thin tail that enables bacteria to swim. We discovered a mutation in a gene that’s critical for growing flagella, which may be the reason for this characteristic.”

Matthew Dorman, first author from the Wellcome Sanger Institute

The soldier was reported to have cholera-like diarrhoea, but researchers now know he was infected with a non-toxigenic strain of V. cholerae. The team discovered genes that may have been responsible for producing a toxin that caused diarrhoea, but are unsure whether such diarrhoea would be classified as choleraic.

Researchers also found that this strain of V. cholerae possessed a gene for ampicillin resistance. This adds to increasing evidence that genes for antibiotic resistance in bacteria existed before the introduction of antibiotic treatments, possibly because the bacteria needed them to protect against naturally-occurring 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.”

Julie Russell, Head of Culture Collections at National Collection of Type Cultures (NCTC)

Notes to Editors

*Founded in 1920, NCTC is one of four Culture Collections of Public Health England that supplies over 5,000 type and reference bacterial strains of medical, scientific and veterinary importance.

Publication:

Matthew Dorman et al. (2019) The history, genome and biology of NCTC 30: a non-pandemic Vibrio cholerae isolate from World War One. Proceedings of the Royal Society B. DOI: 10.1098/rspb.2018.2025

Funding:

This study was supported by Wellcome (206194).

Selected Websites
Science in a conflict zone: Investigating cholera in YemenSanger ScienceScience in a conflict zone: Investigating cholera in Yemen
In addition to the civil war, Yemen is experiencing the worst epidemic of cholera ever recorded. We spoke to Ankur Rakesh, a volunteer doctor with Médecins Sans Frontières (MSF) / Doctors Without B…

Science in the time of choleraStoriesScience in the time of cholera
Although cholera is commonly thought to be a disease of the Victorian era, it is still a significant problem in many areas of the modern world. Genomics research is helping to bring us closer to understanding how we may eliminate it once and for all. 

What are infectious diseases?FactsWhat are infectious diseases?
Infectious diseases are caused by microorganisms such as viruses, bacteria, fungi or parasites and can spread between individuals. 

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