Bacteria in Breasts Linked to Breast Cancer

(Last Updated On: March 13, 2018)
breast cancer linked to bacteria

Metastatic breast cancer. Image by Yale Rosen

Are bacteria invading the breasts of women? Actually, yes and no. Bacteria inhabit all women’s breasts – and have been for millions of years.

Hopefully these breast bacteria are the good kind, mind you. Some of the same species of bacteria that also inhabit our guts will inhabit breast tissues. This is why breast milk is such a good source of early oral and gut probiotics for babies.

But now we find that species of bad bacteria can also inhabit the breast tissues of women. And it turns out that breast cancer is linked with these species of bad bacteria.

Are we sure that bacteria are in women’s breasts?

Yes. A 2014 study from London’s Lawson Health Research Institute and Ontario’s Western University analyzed the breast tissues of 81 women. The breast tissues were collected from breast surgeries – either for cancer or for breast augmentation/reduction procedures.

The researchers conducted DNA sequencing on each breast tissue sample to determine the species of bacteria that inhabited the breast tissues. DNA sequencing has previously been used to determine bacteria residing in the digestive tract. These analyses have been contributed to our knowledge of what is now called our microbiome – the genetic makeup of our resident microbes.

After their DNA analysis, the researchers found that the breasts of the Canadian women contained numerous strains and species of bacteria. These included:

• Bacillus (11.4%)
• Acinetobacter (10.0%)
• Enterobacteriaceae (8.3%)
• Pseudomonas (6.5%)
• Staphylococcus (6.5%)
• Propionibacterium (5.8%)
• Comamonadaceae (5.7%)
• Gammaproteobacteria (5.0%)
• Prevotella (5.0%)

Read more:  Flax Alters Gut Bacteria, Reduces Insulin Resistance

Interestingly, the breasts of the Irish women contained a different combination of strains and species. Most abundant were:

• Enterobacteriaceae (30.8%)
• Staphylococcus (12.7%)
• Listeria welshimeri (12.1%)
• Propionibacterium (10.1%)
• Pseudomonas (5.3%)

That is a significant difference of species between the two countries. But what all the women had in common was that every breast tissue contained numerous species of bacteria.

Of these, some were probiotic – helpful to the body. Others were pathogenic – disease causing. Still others were eubiotic – neither helpful or harmful (theoretically – as this is based upon current research to date.)

As these same researchers continued to test the breast tissues of the subjects, they also discovered that certain species and strains were in fact, linked to breast cancer.

Some breast bacteria linked to cancer

The 2016 study was published in the Applied and Environmental Microbiology, a journal of the American Society for Microbiology. The researchers, from Ireland’s University College Cork and Canada’s Western University, again analyzed the breast tissues from 81 women. This time, they investigated species in relation to breast cancer. Of the women tested, 58 had breast cancer and 23 were women with no history of breast cancer. Of the 58 women who had breast cancer, 13 had benign tumors.

The researchers found that women who had breast cancer had increased colonies of Escherichia coli and Staphylococcus epidermidis and reduced levels of Lactobacillus and Streptococcus species of bacteria.

The healthy women, on the other hand, had increased colonies of Lactobacillus and Streptococcus species. They also had reduced colonies of Escherichia coli and Staphylococcus epidermidis.

Why are these bacteria bad?

Both Escherichia coli and Staphylococcus epidermidis bacteria have been implicated in a number of disease conditions. But specific to cancer, these have also been shown in other studies to produce double-stranded DNA breaks among cells. Double-stranded break results have been seen in laboratory studies of human cultured HeLa cells.

Read more:  Nutrition Critical to Cancer Treatment

The researchers wrote:

“Double-strand breaks are the most detrimental type of DNA damage and are caused by genotoxins, reactive oxygen species, and ionizing radiation.”

ProbioticsBook by Case Adams Naturopath

What’s a genotoxin?

A genotoxin is a substance that causes DNA damage. The result of the DNA damage is a mutation of the DNA. Such a mutation can produce a cancerous cell.

There multiple forms of DNA damage. These can include single- or double-strand breaks. The latter is more serious. Other DNA damage includes cross-link damage and repair blocking issues.

The E. coli and S. epidermidis bacteria may be considered genotoxic, but their primary concern is they produce genotoxic chemicals. And it is these genotoxic chemicals that gain access to the cells’ DNA to produce their damage.

As mentioned, E. coli and S. epidermidis produce other disease conditions within the body. These range from urinary tract and kidney infections to lung and digestive conditions.

Why are Lactobacillus and Streptococcus bacteria good?

This is not a quick answer. These types of bacteria have been symbiotically existing within the human body for millions of years. They promote the body’s health and help protect the body from disease.

This is once again proven in this study of breast cancer. When probiotic bacteria such as Lactobacilli and Streptococci are more prominent in the breast tissues, the risk of breast cancer goes down.

These bacteria modulate the immune system. Among other things, the bacteria will stimulate natural killer cells, which are important for controlling cancer cells. Streptococci species such as S. thermophilus will also produce antioxidants to neutralize reactive oxygen species. These also damage DNA and cause cancer mutations.

probiotics and microbes webinar

Does lactation increase beneficial bacteria?

Chief researcher Dr. Gregor Reid is a professor of surgery, microbiology and immunology at Western University of Ontario. He is also the director of the Canadian Centre for Human Microbiome and Probiotic Research at Lawson Health Research Institute in London and Ontario. Dr. Reid stated,

“Since human milk contains beneficial bacteria, we wondered if they might be playing a role in lowering the risk of cancer. Or, could other bacterial types influence cancer formation in the mammary gland in women who had never lactated? To even explore the question, we needed first to show that bacteria are indeed present in breast tissue.”

Yet Dr. Reid comments that lactation may not be required to promote probiotic species:

“Colleagues in Spain have shown that probiotic lactobacilli ingested by women can reach the mammary gland. Combined with our work, this raises the question, should women, especially those at risk for breast cancer, take probiotic lactobacilli to increase the proportion of beneficial bacteria in the breast? To date, researchers have not even considered such questions, and indeed some have balked at there being any link between bacteria and breast cancer or health.”

The bottom line is that probiotic supplements and probiotic foods are accepted across the board as safe strategies to assist our health.

Read more:  Legumes Reduce Colorectal Cancer Risk


Urbaniak C, Gloor GB, Brackstone M, Scott L, Tangney M, Reid G. The Microbiota of Breast Tissue and Its Association with Breast Cancer. and Its Association with Breast Cancer. and Its Association with Breast Cancer. Appl Environ Microbiol. 2016 Jul 29;82(16):5039-48. doi: 10.1128/AEM.01235-16.

Urbaniak C, Cummins J, Brackstone M, Macklaim JM, Gloor GB, Baban CK, Scott L, O’Hanlon DM, Burton JP, Francis KP, Tangney M, Reid G. Microbiota of human breast tissue. Appl Environ Microbiol. 2014 May;80(10):3007-14. doi: 10.1128/AEM.00242-14.

Adams C. Probiotics-Protection Against Infection: Using Nature’s Tiny Warriors To Stem Infection and Fight Disease. Logical Books, 2016

Case Adams, PhD

Case Adams has a Ph.D. in Natural Health Sciences, is a California Naturopath and is Board Certified as an Alternative Medicine Practitioner, with clinical experience and diplomas in Aromatherapy, Bach Flower Remedies, Blood Chemistry, Clinical Nutritional Counseling, Homeopathy and Colon Hydrotherapy. He has authored 27 books and numerous articles on print and online magazines. Contact: [email protected]

This Site is Copyright Protected.