Cytotoxin K

Cytotoxin-K (CytK) is a protein toxin produced by the gram-positive bacteria Bacillus cereus. It was first discovered in a certain Bacillus cereus strain which was isolated from a food poisoning epidemic that occurred in a French nursing home in 1998. There were six cases of bloody diarrhea, three of which were fatal. None of the known enterotoxins from B. cereus could be detected at this time. Later, this B. cereus strain and its relatives were classified as a brand-new species called Bacillus cytotoxicus, which is the thermo-tolerant member of the B. cereus genus. The cytotoxin-K gene is present in approximately 50% of Bacillus cereus isolates, and its expression is regulated by several factors, including temperature and nutrient availability.

Further studies showed that Cytotoxin-K is a pore-forming toxin that can create small holes in cell membranes, leading to cell death. It has been shown to cause damage to intestinal epithelial cells, indicating its potential role in the pathogenesis of Bacillus cereus infections in humans. The toxicity in humans has not been studied in detail but CC50 values of 500-1000nM dTHP-1 cells. In addition, CytK has been shown to have hemolytic activity, meaning it can damage red blood cells.

In addition to its role in Bacillus cereus pathogenesis, Cytotoxin-K has also been studied for its potential as a diagnostic tool for detecting Bacillus cereus contamination in food products. PCR methods have been analyzed that can detect the presence of CytK in food samples, showing CytK detection could be used for rapid and sensitive detection of potentially contaminated products.

Overall, the discovery and characterization of CytK have led to a greater understanding of the virulence factors of Bacillus cereus and have provided insights into potential targets for detecting, preventing and treating Bacillus cereus infections in humans.