The human body plays host to millions of microorganisms, with different forms collecting and concentrating on various parts or systems of the body. We rely on them for our health as strongly as they rely on us. A recent Canadian study discovered that the microbiota of the female breast is unique, consisting of a population mix that appears nowhere else on the rest of the body. The discovery leaves the researchers asking the question, why.

Breastfeeding babyMicrobiota is a collective term that includes bacteria, viruses, and fungi that inhabit a specific area, or microbiome. Camilla Urbaniak led the study of the female breast microbiota at the University of Western Ontario (UWO), Canada, where she is a PhD candidate.

The UWO research team examined breast tissue from 81 women between 18 and 90 years of age. Some of the women had nursed children at some point in their lives but others had not. Some of them had breast cancer but others did not. All the women were from either Canada or Ireland.

Of the 81 women, ten had undergone breast reduction procedures, so their healthy, cancer-free tissue samples were on file for examination. The tissue from these ten women was used as the control. The remaining 71 women had experienced either benign or cancerous breast tumors so tissue samples of their breasts were available for study. The tissue samples from the 71 women were all taken from a distance about 5 centimeters (2 inches) from the tumor, an area known as "normal adjacent" tissue.

The strains of bacteria found in abundance in the tissue samples of the women free of cancer included Proteobacteria, Lactobacillus, and Bifidobacteria. These particular forms of bacteria are considered beneficial.

Proteobacteria, the most dominant phylum of bacteria in the healthy breast tissue, is also the most dominant phylum in human milk. It metabolizes fatty acids, produced in high concentrations in the breast.

Bifidobacteria and Lactobacillus are beneficial to gastrointestinal (GI) health. Its presence in breast tissue and milk suggests that it protects both mother and child. Babies have no immune system at birth but breast milk supplies the microbiota the baby uses to establish its own beneficial GI microbiome. Formula-fed babies have different GI microbiomes than breast-fed babies.

The bacteria in the tissue samples taken from cancer patients consisted mostly of Bacillus and Escherichia. Different species of Bacillus cause anthrax and food poisoning, among other ailments. Escherichia is known to cause cancer and genetic mutations in the GI tract and bladder.

Urbaniak would like to see further study of how this unique breast microbiome is established, how it influences health for women and their babies, and why the microbiota balance is different in cancerous and noncancerous breast tissue.

Source: Urbaniak, Camilla, et al. "Bacterial microbiota of human breast tissue." Applied and Environmental Microbiology. American Society for Microbiology. Mar 7, 2014. Web. Apr 10, 2014.