Cancer bacteria are bacteria

Bacteria

Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

l 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 carcinogen

Carcinogen

A carcinogen is any substance, radionuclide, or radiation that is an agent directly involved in causing cancer. This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes...

ic. The strongest evidence to date involves the bacterium H. pylori and its role in gastric cancer.

Oncovirus

Oncovirus

An oncovirus is a virus that can cause cancer. This term originated from studies of acutely-transforming retroviruses in the 1950–60s, often called oncornaviruses to denote their RNA virus origin. It now refers to any virus with a DNA or RNA genome causing cancer and is synonymous with "tumor...

es are viral

Virus

A virus is a small infectious agent that can replicate only inside the living cells of organisms. Viruses infect all types of organisms, from animals and plants to bacteria and archaea...

 agents that are similarly suspected of causing cancer.

Known to cause cancer

Helicobacter pylori

Helicobacter pylori

Helicobacter pylori , previously named Campylobacter pyloridis, is a Gram-negative, microaerophilic bacterium found in the stomach. It was identified in 1982 by Barry Marshall and Robin Warren, who found that it was present in patients with chronic gastritis and gastric ulcers, conditions that were...

colonizes the human stomach

Stomach

The stomach is a muscular, hollow, dilated part of the alimentary canal which functions as an important organ of the digestive tract in some animals, including vertebrates, echinoderms, insects , and molluscs. It is involved in the second phase of digestion, following mastication .The stomach is...

 and duodenum

Duodenum

The duodenum is the first section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In fish, the divisions of the small intestine are not as clear and the terms anterior intestine or proximal intestine may be used instead of duodenum...

. In some cases it can cause stomach cancer

Stomach cancer

Gastric cancer, commonly referred to as stomach cancer, can develop in any part of the stomach and may spread throughout the stomach and to other organs; particularly the esophagus, lungs, lymph nodes, and the liver...

 and MALT lymphoma

MALT lymphoma

MALT lymphoma is a form of lymphoma involving the mucosa-associated lymphoid tissue , frequently of the stomach, but virtually any mucosal site can be afflicted...

. Animal models have demonstrated Koch's third and fourth postulates

Koch's postulates

Koch's postulates are four criteria designed to establish a causal relationship between a causative microbe and a disease. The postulates were formulated by Robert Koch and Friedrich Loeffler in 1884 and refined and published by Koch in 1890...

 for the role of Helicobacter pylori in the causation of stomach cancer.

Speculative links

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

Carcinogenesis

Carcinogenesis or oncogenesis is literally the creation of cancer. It is a process by which normal cells are transformed into cancer cells...

 is unclear.

Bacteria	Suggested link
Salmonella typhi	is associated with gallbladder cancer Gallbladder cancer Gallbladder cancer is a relatively uncommon cancer. It has peculiar geographical distribution being common in central and South America, central and eastern Europe, Japan and northern India; it is also common in certain ethnic groups e.g. Native American Indians and Hispanics. If it is diagnosed... .
Streptococcus bovis Streptococcus bovis Streptococcus bovis is a catalase- and oxidase-negative, non-motile, non-sporulating, Gram-positive lactic acid bacterium that grows as pairs or chains of cocci. It is a member of the Lancefield group D streptococci. Most strains are non- or gamma-hemolytic, but some also display alpha-hemolytic...	is associated with colorectal cancer Colorectal cancer Colorectal cancer, commonly known as bowel cancer, is a cancer caused by uncontrolled cell growth , in the colon, rectum, or vermiform appendix. Colorectal cancer is clinically distinct from anal cancer, which affects the anus.... .
Chlamydia pneumoniae	is associated with lung cancer Lung cancer Lung cancer is a disease characterized by uncontrolled cell growth in tissues of the lung. If left untreated, this growth can spread beyond the lung in a process called metastasis into nearby tissue and, eventually, into other parts of the body. Most cancers that start in lung, known as primary... .
Mycoplasma Mycoplasma Mycoplasma refers to a genus of bacteria that lack a cell wall. Without a cell wall, they are unaffected by many common antibiotics such as penicillin or other beta-lactam antibiotics that target cell wall synthesis. They can be parasitic or saprotrophic. Several species are pathogenic in humans,...	may also have a role in the formation of different types of cancer.
H. pylori	has been linked with certainty to stomach cancer and may be related to MALT lymphoma MALT lymphoma MALT lymphoma is a form of lymphoma involving the mucosa-associated lymphoid tissue , frequently of the stomach, but virtually any mucosal site can be afflicted... , but may also protect certain individuals from esophageal cancer Esophageal cancer Esophageal cancer is malignancy of the esophagus. There are various subtypes, primarily squamous cell cancer and adenocarcinoma . Squamous cell cancer arises from the cells that line the upper part of the esophagus... .

Salmonella typhi

Salmonella enterica enterica

Salmonella enterica enterica is a subspecies of Salmonella enterica, the rod shaped, flagellated, aerobic, Gram-negative bacterium. It is a member of the genus Salmonella. Many of the pathogenic serovars of the S...

has been linked to gallbladder cancer

Gallbladder cancer

Gallbladder cancer is a relatively uncommon cancer. It has peculiar geographical distribution being common in central and South America, central and eastern Europe, Japan and northern India; it is also common in certain ethnic groups e.g. Native American Indians and Hispanics. If it is diagnosed...

 but may also be useful in delivering chemotherapeutic agents for the treatment of melanoma

Melanoma

Melanoma is a malignant tumor of melanocytes. Melanocytes are cells that produce the dark pigment, melanin, which is responsible for the color of skin. They predominantly occur in skin, but are also found in other parts of the body, including the bowel and the eye...

, colon and bladder cancer

Bladder cancer

Bladder cancer is any of several types of malignant growths of the urinary bladder. It is a disease in which abnormal cells multiply without control in the bladder. The bladder is a hollow, muscular organ that stores urine; it is located in the pelvis...

. 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

Chronic (medicine)

A chronic disease is a disease or other human health condition that is persistent or long-lasting in nature. The term chronic is usually applied when the course of the disease lasts for more than three months. Common chronic diseases include asthma, cancer, diabetes and HIV/AIDS.In medicine, the...

 inflammation

Inflammation

Inflammation is part of the complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. Inflammation is a protective attempt by the organism to remove the injurious stimuli and to initiate the healing process...

, may also be linked to oral cancer

Oral cancer

Oral cancer is a subtype of head and neck cancer, is any cancerous tissue growth located in the oral cavity. It may arise as a primary lesion originating in any of the oral tissues, by metastasis from a distant site of origin, or by extension from a neighboring anatomic structure, such as the...

s.

The relationship between cancer and bacteria may be complicated by different individuals reacting differently to different cancers.

History

In 1890, the Scottish pathologist William Russell reported circumstantial evidence for the bacterial cause of cancer. In 1926, Canadian physician Thomas Glover reported that he could consistently isolate a specific bacterium from the neoplastic tissues of animals and humans. One review summarized Glover's report as follows:
Glover was asked to continue his work at the Public Health Service (later incorporated into the National Institutes of Health) completing his studies in 1929 and publishing his findings in 1930. He asserted that a vaccine or anti-serum manufactured from his bacterium could be used to treat cancer patients with varying degrees of success. According to historical accounts, scientists from the Public Health Service challenged Glover’s claims and asked him to repeat his research to better establish quality control. Glover refused and opted to continue his research independently; not seeking consensus, Glover's claims and results led to controversy and are today not given serious merit.

In 1950, a Newark based physician named Virginia Livingston

Virginia Livingston

Virginia Livingston was an American physician and cancer researcher who advocated the unsupported theory that a specific species of bacteria she named Progenitor cryptocides was the primary cause of cancer in humans...

 published a paper claiming that a specific Mycobacterium was associated with neoplasia. Livingston continued to research the alleged bacterium throughout the 1950s and eventually proposed the name Progenitor cryptocides as well as developed a treatment protocol. Ultimately, her claim of a universal cancer bacterium was not supported in follow up studies. In 1990 the National Cancer Institute

National Cancer Institute

The National Cancer Institute is part of the National Institutes of Health , which is one of 11 agencies that are part of the U.S. Department of Health and Human Services. The NCI coordinates the U.S...

 published a review of Livingston's theories, concluding that her methods of classifying the cancer bacterium contained "remarkable errors" and it was actually a case of misclassification - the bacterium was actually Staphylococcus epidermidis

Staphylococcus epidermidis

Staphylococcus epidermidis is one of thirty-three known species belonging to the genus Staphylococcus. It is part of human skin flora, and consequently part of human flora. It can also be found in the mucous membranes and in animals. Due to contamination, it is probably the most common species...

.

Later reports were published by other researchers who also claimed to have found bacteria associated with different types of cancers.