The first bacteria that came to my mind on reading your question was Helicobacter pylori. There is quite some literature on it and about its association with different cancers including oral cancer.

The faeco-oral route is one of the modes of transmission of H. pylori, so its association with oral cancer is very much possible.

I found it very appealing and checked it up and found a few articles about it. There have been some work on this too.

As this paper states : "Studies have shown diversity of isolated bacterial taxa between the oral cancer tissue specimens and the control, with Exiguobacterium oxidotolerans, Prevotella melaninogenica, Staphylococcus aureus and Veillonella parvula being specific for tumorogenic tissues. Most isolates are saccharolytic and acid tolerant. Streptococcus anginosus, commonly linked with esophageal and pharyngeal cancers, is not of significance in oral cancers. Similarly, significant salivary specificity is noted for three bacteria, namely, Capnocytophaga gingivalis, P. melaninogenica, and Streptococcus mitis in oral cancer patients, making these species salivary markers for the early detection of oral cancers and thus improving the survival rate significantly. Also, such high degree of bacterial specificity in oral cancers has also provoked the designing of new treatment options for cancer prevention by way of vaccine delivery. However, for the success of these steps, a deeper exploration into this subject with a greater understanding is warranted."

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3089920/

This is another one from JADA by the researchers from Forsyth institute. They also state that Capnocytophaga gingivalis, P. melaninogenica, and Streptococcus mitis have been seen in association with oral cancer.

http://jada.ada.org/content/136/9/1222.1.full

Thank you all for the interesting articles which were a research article and a review and a comment on the research article. It seems that different researches have detected different bacterial species. I am also concerned about other variables that may influence the results like periodontal condition since gingivitis and periodontitis have a major influence on the type of microbiota colonizing the oral cavity. It is a well-known fact that oral cancer patients tend to neglect oral hygiene.

Dr. Dar-Odeh,

In the first article and each one of them these three are the highlight : Capnocytophaga gingivalis, P. melaninogenica, and Streptococcus mitis

Exclusion criteria of the study at Forsyth study for microbiota as salivary biomarker included: antibiotic therapy within the previous 3 months, pregnancy or lactation, systemic conditions associated with immune dysfunction (e.g., diabetes), previous chemotherapy or radiation and the presence of any oral mucosal lesions.

The results were 80%+ for it, what next could be done is comparison with smokers, immunocompromized, diabetic, pregnant etc can be done and an array of overlapping conditions for the same can be made. I see a lot of potential in this one.

Thank you Anirudha. I think that we need more studies to confirm this association. In the comment you posted it was mentioned that the research team will further study this issue to validate the results. Do you think that they did that?

I strongly feel that alcohol consumption can be an adding factor because many times alcohol coulbe be turned to acteldehyde by bacterial activity leading to oral cancers

I strongly feel that alcohol consumption can be an adding factor because many times alcohol coulbe be turned to acteldehyde by bacterial activity leading to oral cancers

The first bacteria that came to my mind on reading your question was Helicobacter pylori. There is quite some literature on it and about its association with different cancers including oral cancer.

The faeco-oral route is one of the modes of transmission of H. pylori, so its association with oral cancer is very much possible.

I agree with you Ahed regarding the cause-effect relationship. A very interesting theory from your side Jayachandran and Rishikesh. To my colleagues who are expert in molecular biology: how can bacteria cause cancer?

Dear Dr Najla,

Another interesting finding is the ingrowth of the candidal hyphae into the oral epitehlium in chronic hyperplastic candidosis is a skyrocketing factor.

Virus lead to abrogation of p53 and pRb tumour suppressor genes leading to alteration in host genome thereby leading to oral cancers.

Chronic inflammation as in in peridontitis can also be an additive factor

You might find this of interest

http://microbiologyworld.com/stem-cells-found-in-gum-tissue-can-fight-inflammatory-disease/

Thank you Buenaflor. It is an informative link. Does it have anything on bacteria-cancer relationship?

One of the study suggests a high levels of three bacterial species namely C. gingivalis, P. melaninogenica and S. mitis in the oral cancer patients. However, the role of bacteria in cancer has to probed in directions of causative or coincidence ?

Please find the attached published report which would be helpful in the research direction.

Article Bacteria and cancer: Cause, coincidence or cure? A review

The inflammation by long-lived bacterial infection may cause cancer. For details please visit the article.

http://www.ncbi.nlm.nih.gov/pubmed/20303878

I have read the article with great interest. The continuation of research in this field is indispensable.

Thank you Avadhesh. A solid relationship was found between certain infections and cancer. Most of these infective agents are viruses. H pylori is probably the most investigated and proven to be linked with cancer. This is well-detailed in the review of de Martel and Franceschi (2009)

Dear Dr. Najla yes there is a relationship specially the virus infection the question is it causative factor of oral cancer or it is due to low immunity ? HPV is my field it is there is controversy in considering HPV as one of main factor in oral cancer but research done by De"ssosa 2007 by detection of L2 protein in blood of patients in adulthood got HNSCC prove that high % of them with positive L2 ,but still more researches including the socio- geographic difference and the genetic profile is needed to confirm this , that oral cancer is multifactorial disease the bacteria ,fungus,and viruses could have a role

Yes, the human papilloma virus is now linked to head n neck cancer in a huge number of cases all over the world.

I had a patient , 21 years old, had no habits and no sharp teeth.she had a large ulcer on the posterior third of the tongue, on the lateral border, extending upto the base.she had palpable, fixed cervical lymph nodes.

Her biopsy report showed well-differentiated squamous cell carcinoma.

I discussed this with my oncologist, and with the pathologist from the breach candy hospital.

Both concurred that the possible cause could be human papilloma virus and there would be history of sexual contact.

I questioned the patient and it was true.

in fact, in many hospitals, tests are done now to determine status of p16 oncoprotein in all oral and oropharyngeal carcinomas. Furthermore it has been observed that HPV related carcinomas mostly present in early T category but usually have cervical lymph node metastases.

Maura L. Gillison, MD, PhD, of Johns Hopkins University in Baltimore, has been an HPV researcher for a long time.

she has published many of her findings, so you can look them up for more details.

Thank you Maha and Arnavaz. The cancer-HPV relationship is important especially in oral cancer. The question is : is the same relationship confirmed between CA and bacteria?

As far as I know, we have two situations; Oncogenic factors, like Tobacco and Risk factors, like sharp teeth and bad oral hygienis. We have to remind that cancer happens after an DNA alteration, so a bacteria have to act directly in the DNA to be considered a cancer causer. But we can also make a link if we think bacterial colonization may cause cronic inflammation, and so be a risk factor for Oral cancer. Till the moment no bacteria can be pointed with a consistent relation with oral cancer, and the levels of H. pylori in the Oral cavity are insicnificant to make some link. Thank you all for the answers greetings from RIO

Thank you Alexandre for your answer. I agree with you that the link between oral cancer and bacteria is not confirmed yet. I question though the link that you proposed between poor oral hygiene and sharp teeth on one hand and oral cancer on the other hand. It will be a disaster if people get oral cancer because of their poor oral hygiene! Generally speaking, oral cancer rates in third world countries , excepting India, is lesser than developed countries, although the standard of oral care is much better in industrialized countries. The reasonable explanation for me is the negative social habits like smoking, alcohol and promiscuity.

The answer is "Yes". Please go through the following RG links.

Article Oral bacterial flora and oral cancer: The possible link?

Article The role of bacteria in oral cancer

Article Emerging role of bacteria in oral carcinogenesis: A review w...

Article Helicobacter pylori and Oral Cancer: Possible Association in...

Article Variations in oral microbiota associated with oral cancer

Article Changes in Abundance of Oral Microbiota Associated with Oral Cancer