He was not one for crowds or the limelight. Yet, through a series of painstaking experiments in a Calcutta laboratory, Sambhu Nath De changed the way the world understood cholera. His discovery of the toxin behind the disease would go on to influence generations of research, even as recognition for his work remained limited in his own country.
In the 1950s, cholera remained a major public health threat, and scientists were still trying to understand how the disease caused such severe fluid loss. The prevailing explanation focused on the bacteria entering the bloodstream. De, however, believed the answer lay in the intestine. It was an unconventional line of inquiry, but he pursued it through a series of carefully designed experiments.
Born in 1915 in Garibati, a village on the western bank of the Ganga, De grew up amid financial hardship after floods ruined his family’s business. His uncle, Ashutosh De, encouraged his education and helped him continue his studies. De passed his matriculation examination with distinction and won a scholarship to Hooghly Mohsin College. He graduated in medicine from Calcutta Medical College in 1939, obtained a Diploma in Tropical Medicine in 1942 and went on to earn a PhD in pathology from University College Hospital Medical College, London, in 1949.
After returning to India, he worked at Nil Ratan Sarkar Medical College before becoming head of pathology and bacteriology at Calcutta Medical College. Alongside his academic work, he began investigating the effects of Vibrio cholerae on the intestinal lining.
Using the rabbit ileal loop model, De demonstrated that a bacteria-free culture filtrate of V cholerae could cause fluid to accumulate in the intestine, even when the bacteria themselves were absent. This pointed to a toxin released by the bacteria, rather than invasion of the bloodstream, as the cause of cholera’s characteristic fluid loss.
In 1959, he published his landmark findings in Nature in a paper titled ‘Enterotoxicity of bacteria-free culture filtrate of Vibrio cholerae’. The work established the role of cholera toxin and helped shape subsequent research into enterotoxin-producing Escherichia coli. The discovery brought De international recognition. Nobel laureate Joshua Lederberg nominated him for the Nobel Prize. In 1978 De was invited to the 43rd Nobel Symposium on Cholera and related subjects. Yet his contribution remained relatively unknown in India.
De preferred a close circle of friends to large gatherings and conventions. He retired in 1973, but continued to help patients and set up a clinical pathology laboratory at home. He died on April 15, 1985. His discovery reshaped cholera research; the scientist behind it, however, remained far less familiar than his work.
