In 1916, a British soldier who fought in World War I was recuperating in Egypt after suffering cholera-like symptoms. Historic observations concluded the cholera bacteria in his system was unusual: it was antibiotic resistant and lacked flagellum, the appendage that allows the bacteria to move. The specimen is now believed to be the oldest “live” sample of Vibrio cholerae in existence; it had been freeze-dried in storage at England’s National Collection of Type Cultures since 1920.
Now, researchers at Public Health England and the Wellcombe Sanger Institute have sequenced the genome of the bacteria, providing insight into how the complex pathogen has changed over time, reports Kate Kelland at Reuters.
Cholera is a bacterial infection that can cause life-threatening diarrhea, in addition to intense vomiting and leg cramps. The Center for Disease Control estimates that “2.9 million cases and 95,000 deaths” occur globally each year. The infection is often mild or without symptoms, but in severe cases, “death can occur within hours,” according to the CDC.
Since 1817, there have been seven global cholera pandemics, including the current one that’s been going on since 1961. World War I happened during the sixth global cholera epidemic, which lasted from 1899 to 1923. Over two centuries, the quickly-mutating disease has thwarted efforts to control it.
Surprisingly, the cholera strain that the team sequenced called NCTC 30 turned out to be non-toxigenic, meaning it could not cause an infection and therefore, probably wasn’t the source of the soldier’s symptoms, Genomeweb reports. It was, however, still distantly related to cholera strains that initiated previous epidemics, including the one happening now. The new study appears in the journal Proceedings of the Royal Society B.
“[U]nder the microscope, the bacterium looks broken; it lacks a flagellum—a thin tail that enables bacteria to swim,” study co-author Matthew Dorman, a graduate student at the Sanger Institute, says in a statement. “We discovered a mutation in a gene that's critical for growing flagella, which may be the reason for this characteristic."
NCTC 30 is also resistant to antibiotics, including penicillin. In fact, it’s possible that these bacteria learned how to fight off naturally-occurring antibiotics before Alexander Fleming isolated penicillin in 1928. According to the press release, this finding supports an emerging theory that some diseases developed antibiotic resistant capabilities even before humans discovered the class of drugs.
“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,” lead author Nick Thomson of the Wellcombe Sanger Institute says in a statement. “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."