Table 2.

Bacterial species found to be associated with the microbiota of breast cancer tissue, in patients, and in murine models and their function in the progression of breast cancer.

Breast Cancer Tissue	Bacteria	Molecular Mechanism	Reference
Human	Escherichia coli and Staphylococcus	Induction of DNA double-strand break and genomic instability in vitro	[14]
Human	Clostridiales	Inhibition of tumor growth by producing the metabolite trimethylamine N-oxide (TMAO) that activates CD8+ T cells- mediated antitumor-immunity	[53]
Human	Fusobacterium nucleatum	Breast tumor progression and metastases by fap-2 dependent binding of the bacterium to breast cancer tissue Gal-GalNac	[68]
Mice	Staphylococcus, Lactobacillus and Streptococcus	Breast tumor lung metastases by modulating the stress response and influencing cancer cell viability, altering the cell cytoskeleton	[15]
Mice	Staphylococcus epidermidis	Increased T regulatory cell infiltration in the tumor and complement pathway activation in vivo, and increased pro-tumoral M2 macrophages phenotype in vitro	[16]
Mice	Micrococcus luteus	Reduction of mammary tumor growth in vivo, and increased anti-tumoral M1 macrophage phenotype in vitro	[16]
Mice	Bacteroides fragilis	Breast tumor progression and metastasis through the secretion of the B. fragilis toxin (BFT)	[65]