Bacterial infections trigger chronic inflammation that alters cell growth and induces tumors. Bacteria H. pylori is linked to gastric cancer; S. typhi to gall bladder cancer; S. bovis to colon cancer; C. pneumoniae to lung cancer. P. melaninogenica, S. mitis are early salivary markers in the detection of oral cancers while C. trachomatis is linked to a higher risk of cervical cancer.
Bacterial infections and cancer, now that’s a connection that has mystified and challenged science for ages. Nineteenth century New York surgeon William Coley, better known as the “Father of Cancer Immunology,” was the first to suggest that parasitic microorganisms could cause cancer. The 20th century saw several controversies around the bacteria–cancer conundrum. The bacterial theory of cancer was finally proven in the early 2000s when cancer biologists established a link between the bacterium Helicobacter pylori and gastric cancer.
Today, research shows a clear connection between bacteria, the inflammation they cause, and several kinds of cancer. In fact, around 15–20% of all cancers can be traced to chronic inflammation.1
The Connecting Link
So how can a bacterial infection lead to cancer? The bacteria by themselves don’t cause cancer – rather, the chronic inflammation they trigger are to blame. Bacteria can produce infections and toxins which alter cell growth and disturb normal development of the cells.2 These chronic infections accelerate cell transformation and thereby induce tumors.
Which Bacteria Can Cause Cancer?
- Helicobacter pylori: Almost two-third of the world is believed to carry these bacteria found in the stomach.3 H. pylori is responsible for chronic, persistent gastritis and is linked to gastric cancer.4 In 1994, the International Agency for Research on Cancer classified the bacteria as a carcinogen.5 H. pylori also causes a rare gastric lymphoma. The stomach lining does not normally have lymph tissue, but the presence of H. pylori in the lining leads to this growth.6
- Salmonella typhi: These bacteria causes typhoid. Research evidence suggests that a chronic infection of S. typhi has a bearing on gall bladder cancer (GBC). In a 2010 study, 33% of the GBC cases studied were also co-infected with S. typhi.7
- Capnocytophaga gingivalis, P. melaninogenica, and Streptococcus mitis: All of these bacteria live and thrive in the saliva and mouth. These are early salivary markers in the detection of oral cancers. Early testing for these bacteria in saliva can improve prognosis and outlook.8
- Chlamydia trachomatis: A common bacterial infection, it affects the female reproductive system. It can cause vaginal and urinary infections. These bacteria do not usually produce symptoms and affected women are diagnosed only during a routine pelvic exam. The infection usually spreads through sex, with sexually active women being more prone to it. Research studies indicate that current or past infections of C. trachomatis are associated with a higher risk of cervical cancer.9 One study of 1238 cases of cervical cancer showed that the risk was higher in women who tested positive for C. trachomatis.10
- Chlamydia pneumoniae: There is clear evidence of the link between C. pneumoniae and lung cancer. These bacteria cause pneumonia and are generally found in the bronchial lining of the lungs. In a study of 230 smoking males with lung cancer, markers suggested the presence of C. pneumoniae in 52% of the cases.11
- Streptococcus bovis: These bacteria find a good host in the human digestive tract and are common in the mouth, food pipe, stomach, and small and large intestines. The connection between S. bovis and colon cancers has been under the scanner since the 1970s.12 Rat studies clearly indicate that S. bovis has a role in cancer growths in the colon.13
Now that we have a fair idea of the bacteria associated with cancers, address these bacterial infections in the early stages and avoid the harmful effects of chronic inflammation and infection. If you suspect any bacterial infection, see a physician immediately and get a blood or tissue culture to determine the bacterial species. Early intervention is your best bet in the fight against bacterial infections and their long-term carcinogenic effects.
References [ + ]
|1.||↑||Do Bacteria Cause Cancer? Cancer Research Institute.|
|2.||↑||Chocolatewala, N., Chaturvedi, P. and Desale, R., 2010. The role of bacteria in oral cancer. Indian Journal of Medical and Paediatric Oncology, 31(4), p.126.|
|3.||↑||Helicobacter pylori, Center for Disease Prevention and Control.|
|4.||↑||Parsonnet, Julie. “Bacterial infection as a cause of cancer.” Environmental health perspectives 103, no. Suppl 8 (1995): 263.|
|5.||↑||Correa, Pelayo. “Bacterial infections as a cause of cancer.” Journal of the national cancer Institute 95, no. 7 (2003): E3-E3.|
|6.||↑||Helicobacter pylori and Cancer, National Cancer Institute.|
|7.||↑||Tewari, Mallika, Raghvendra R. Mishra, and Hari S. Shukla. “Salmonella typhi and gallbladder cancer: report from an endemic region.” Hepatobiliary Pancreat Dis Int 9, no. 5 (2010): 524-530.|
|8.||↑||Chocolatewala, Noureen, Pankaj Chaturvedi, and Rushikesh Desale. “The role of bacteria in oral cancer.” Indian Journal of Medical and Paediatric Oncology 31, no. 4 (2010): 126.|
|9.||↑||Koskela, Pentti, Tarja Anttila, Tone Bjørge, Anne Brunsvig, Joakim Dillner, Matti Hakama, Timo Hakulinen et al. “Chlamydia trachomatis infection as a risk factor for invasive cervical cancer.” International journal of cancer 85, no. 1 (2000): 35-39.|
|10.||↑||Smith, Jennifer S., Cristina Bosetti, Nubia MUnoz, Rolando Herrero, F. Xavier Bosch, José Eluf‐Neto, Chris JLM Meijer, Adriaan JC van den Brule, Silvia Franceschi, and Rosanna W. Peeling. “Chlamydia trachomatis and invasive cervical cancer: A pooled analysis of the IARC multicentric case‐control study.” International journal of cancer 111, no. 3 (2004): 431-439.|
|11.||↑||Laurila, Aino L., Tarja Anttila, Esa Laeaerae, Aini Bloigu, Jarmo Virtamo, Demetrius Albanes, Maija Leinonen, and Pekka Saikku. “Serological evidence of an association between Chlamydia pneumoniae infection and lung cancer.” International journal of cancer 74, no. 1 (1997): 31-34.|
|12.||↑||Corredoira, Juan, María Pilar Alonso, Amparo Coira, and José Varela. “Association between Streptococcus infantarius (formerly S. bovis II/1) bacteremia and noncolonic cancer.” Journal of clinical microbiology 46, no. 4 (2008): 1570-1570.|
|13.||↑||Ellmerich, Stéphan, Marie Schöller, Benoît Duranton, Francine Gossé, Michel Galluser, Jean-Paul Klein, and Francis Raul. “Promotion of intestinal carcinogenesis by Streptococcus bovis.” Carcinogenesis 21, no. 4 (2000): 753-756.|