Researchers at the University of Western Ontario investigating female breast tissue have discovered the tissue actually contains a much wider and more unique population of bacterial microorganisms than previously thought.
Tissue samples were taken from 81 women in Canada and Ireland between the ages of 18 and 90. Ten came from women who had undergone breast reduction surgery, and were used as the control, while the other samples were from women who had either benign or cancerous tumours in the past.
They found proteobacteria is the dominant phylum in healthy breast tissue but also detected traces of beneficial bacteria, such as Lactobacillus and Bifidobacteria. Traces of Proteobacteria, which metabolises fatty tissue, are minimal elsewhere in the body, although it is predominant in human milk.
University PhD student Camilla Urbaniak explained: “The presence of proteobacteria may reflect the fact that breast tissue produces high concentrations of fatty acids.”
“The fact that beneficial bacteria were also present makes us wonder whether their presence might be protective for both mother and child. Breast milk is one of the initial sources of gastrointestinal (GI) bacteria for newborns, and their GI microbiota are different if they are formula fed.”
The internal battle again disease
Studies of the microbiome in other parts of the body, and particularly the gastrointestinal tract, have shown that certain changes in bacterial populations can lead to a variety of illnesses, from inflammatory bowel disease to diabetes, obesity, cancer and even neurological conditions.
In the samples taken from women with benign or cancerous tumours, the predominant bacteria were Escherichia and Bacillus, which are known to propagate mutagenic and carcinogenic activity in the gut and bladder. However other pathogens such as Pseudomonas and Streptococcus agalactiae were found in healthy tissue with no adverse side effects.
Urbaniak said: “It is possible that the breast microbiome contributes to maintenance of healthy breast tissue by stimulating resident immune cells, but the type of bacteria and their metabolic activity, such as the ability to degrade carcinogens, may also contribute.
"Future studies will examine how this breast microbiome is established, why no infections accompany colonisation, despite the fact that some of these bacteria cause infections elsewhere in the body, what impact these organisms have on the host, and whether external factors such as diet, antibiotics, and illness affect this bacterial community, and what consequences that has for women and their offspring.”
Published March 2014 in Applied and Environmental Microbiology
‘Bacterial microbiota of human breast tissue’
Authors: Camilla Urbaniak, Joanne Cummins, Muriel Brackstone, Jean M. Macklaim, Gregory B. Gloor, Chwanrow K. Baban, Leslie Scott, Deidre M. O’Hanlon, Jeremy P.Burton, Kevin P. Francis, Mark Tangney, Gregor Reid