Microbiota of the Mammary Gland in Wistar Rats with Chemically Induced Breast Cancer after Treatment

We conducted a comparative study of the mammary gland microbiota in female Wistar rats and the microbiota associated with breast cancer (BC) induced by the administration of N-methyl-N-nitrosourea, after surgical treatment, photodynamic therapy (PDT), and chemotherapy (CT). Selective nutrient media and a smear-fingerprint technique were used to study the microbiota. Staphylococcus, Streptococcus, and Lactobacillus were found in the mammary glands of intact rats. The mean number of Staphylococcus CFU increased statistically significantly in all groups of rats with induced BC, compared to intact animals: by 8 times in the BC without treatment group, by 15% in BC+surgery, by 10 times in BC+PDT, by 4 times in BC+PDT+CT, and by 13 times in BC+CT. The number of Streptococcus CFU also increased in all experimental groups: by 15.5 times in the BC without treatment group, by 4 times in BC+surgery, by 2.6 times in BC+PDT, by 4.5 times in BC+PDT+CT, and by 3.5 times in BC+CT. The number of Lactobacillus CFU significantly increased only in the BC+PDT group (by 2.5 times). The development of the microbiota in the tumor allows evaluating the impact of various types of therapy on the growth of opportunistic microorganisms. The results suggest that doxorubicin combined with PDT has the most potent effect on changes to the tumor microbiota.