PMC

Percent abundances of different bacterial phyla in breast tissue identified by 16S rRNA sequencing. (A) Box plots of the seven different phyla identified in breast tissue from the Canadian and Irish samples. The box signifies the 75% (upper) and 25% (lower) quartiles and thus shows where 50% of the samples lie. The black line inside the box represents the median. The whiskers represent the lowest datum still within 1.5 interquartile range (IQR) of the lower quartile and the highest datum still within 1.5 IQR of the upper quartile. Outliers are shown with open circles. (B) The least-abundant phyla shown in panel A were plotted on another graph with a smaller scale to allow for better visualization of percentage. In samples from both countries Proteobacteria was the most abundant phylum, followed by Firmicutes (Kruskal-Wallis test/Mann-Whitney U test with Bonferroni correction, P ≤ 0.001).

Breast tissue microbiota in 38 Irish women identified, by 16S rRNA sequencing. The relative abundances of bacterial taxa identified in different tissue samples were visualized by bar plots. Each bar represents a subject and each colored box a bacterial taxon. The height of a colored box represents the relative abundance of that organism within the sample. For example, sample C40H is dominated by Janibacter, whereas C36N is dominated by Enterobacteraceae. Taxa present in less than 2% abundance in a given sample are displayed in the “Remaining fraction” at the top of the graph (gray boxes). As shown by the bar plots, a variety of bacteria were detected in breast tissue. The legend is read from bottom to top, as indicated by the red arrow, with the bottom organism on the legend corresponding to the bottom colored box on the bar plot. CH, tissue collected from women undergoing breast reductions; CN, nonmalignant tissue collected adjacent to cancerous tumors.

Breast tissue microbiota in 43 Canadian women, identified by 16S rRNA sequencing. The relative abundances of bacterial taxa identified in different tissue samples were visualized by bar plots. Each bar represents a subject and each colored box a bacterial taxon. The height of a colored box represents the relative abundance of that organism within the sample. For example, sample L42H is dominated by Acinetobacter, whereas L19Nb is dominated by Micrococcus. Taxa present in less than 2% abundance in a given sample are displayed in the “Remaining fraction” at the top of the graph (gray boxes). As shown by the bar plots, a variety of bacteria were detected in breast tissue. The legend is read from bottom to top, as indicated by the red arrow, with the bottom organism on the legend corresponding to the bottom colored box on the bar plot. LH, tissue collected from women undergoing breast reductions; LN, nonmalignant tissue collected adjacent to cancerous tumors; LNb, nonmalignant tissue collected adjacent to benign tumors.

Locations within the breast of tissue samples collected for bacterial analysis. Tissue samples were collected from 43 women from London, Canada, and 38 women from Cork, Ireland, undergoing different breast surgeries. (A and B) Locations of tissue collected from women in Canada undergoing lumpectomies or mastectomies for either malignant (A) or benign (B) tumors. Subject 25 underwent a prophylactic mastectomy due to previous cancer in the other breast. (C) Locations of tissue collected from women in Ireland undergoing lumpectomies or mastectomies for malignant tumors. Blue ovals represent the location of the tumor, and purple squares represent the location of the specimen obtained for bacterial analysis. The distances between the blue ovals and purple squares are approximate estimates of the distance between the tumor and the specimen, which was at least 5 cm away from the tumor. (D) Locations of tissue collected from women in both Canada and Ireland undergoing breast reduction surgery. Asterisks in the purple boxes underneath the subject number indicate samples from Ireland. All samples were a minimum of 1 cm deep into the skin, with the surgeons aiming for mid-deep rather than superficial locations. As shown in the diagram, specimens were obtained from a variety of locations within the breast.