Cancer bacteria

Cancer bacteria are bacteria infectious organisms that are known or suspected to cause cancer. While cancer-associated bacteria have long been considered to be opportunistic (i.e., infecting healthy tissues after cancer has already established itself), there is some evidence that bacteria may be directly carcinogenic. The strongest evidence to date involves the bacterium H. pylori and its role in gastric cancer.

Oncoviruses are viral agents that are similarly suspected of causing cancer.

Helicobacter pylori colonizes the human stomach and duodenum. In some cases it can cause stomach cancer and MALT lymphoma. Animal models have demonstrated Koch's third and fourth postulates for the role of Helicobacter pylori in the causation of stomach cancer. The mechanism by which H. pylori causes cancer may involve chronic inflammation, or the direct action of some of its virulence factors, for example, CagA has been implicated in carcinogenesis.

A number of bacteria have associations with cancer, although their possible role in carcinogenesis is unclear.

Salmonella typhi has been linked to gallbladder cancer but may also be useful in delivering chemotherapeutic agents for the treatment of melanoma, colon and bladder cancer. Bacteria found in the gut may be related to colon cancer but may be more complicated due to the role of chemoprotective probiotic cancers. Microorganisms and their metabolic byproducts, or impact of chronic inflammation, may also be linked to oral cancers.

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