There is growing evidence that certain types of bacteria may cause some cancers, according to a leading expert.
Alistair Lax, professor of cellular microbiology at King's College London, said bacteria may be involved in stomach, renal and bowel cancers.
He said testing for certain bacteria could enable doctors to identify those at risk of cancer much earlier.
He is scheduled to tell scientists that there is now evidence to suspect bacteria in a range of cancers. He will highlight recent studies into Helicobacter pylori. As many as one in three people may carry this bacteria, which can cause stomach ulcers.
But many scientists now believe it may also play a role in stomach cancer.
Professor Lax said this and other bacteria may interfere with cells in the body, causing them to turn cancerous.
Cells in the body are constantly changing. They are growing, dividing or dying off.
However, poisons produced by bacteria can interfere with the communication process that regulates this cycle.