doi:10.1038/nindia.2010.94 Published online 21 July 2010
In contrast with its multifaceted use as a therapeutic agent, curcumin in turmeric has been found to strengthen the defence mechanism of the typhoid bug Salmonella.
The study urges a rethink on the indiscriminate use of curcumin, particularly in Salmonella outbreaks.
Curcumin regulates the defence pathways of Salmonella enterica serovar Typhimurium (S. Typhimurium) to increase its pathogenicity.
The researchers infected mice models with Salmonella and then treated them with curcumin. They observed higher bacterial load in significant regions — Peyer's patches, mesenteric lymph node, spleen and liver. The bug grew three times faster when exposed to curcumin.
Curcumin increased the resistance of S. Typhimurium against antimicrobial agents such as antimicrobial peptides, reactive oxygen and nitrogen. This increased tolerance is thought to have resulted from an increase in a cellular component (upregulation) of genes involved in resistance.
Curcumin is known to downregulate SPI1 genes, which are required for entry into epithelial cells, and upregulate SPI2 genes, which are required for intracellular survival. This means that the bug faces less hindrance when entering the cells and has more chance of surviving inside.
The researchers believe that the high intake of curcumin could be one of the reasons for widespread Salmonella infections in Asian countries.