Comparative studies of the immunogenicity and protective potential of biofilm vs planktonic Staphylococcus aureus vaccine against bovine mastitis using non-invasive mouse mastitis as a model system

This study was undertaken to compare the immunogenicity and protective potential of biofilm vs planktonic Staphylococcus aureus vaccine for the prevention of mastitis using the mouse as a model system. Mice immunized with formalin-killed whole cell vaccine of S. aureus residing in a biofilm when delivered via an intramammary route produced a cell mediated immune response. Mice immunized with this biofilm vaccine showed significant reductions in colonization by S. aureus in mammary glands, severity of clinical symptoms and tissue damage in mammary glands in comparison with the mice immunized with formalin-killed whole cells of planktonic S. aureus. The planktonic vaccine administered by a subcutaneous route produced a significantly higher humoral immune response (IgG₁ and IgG) than the biofilm vaccine. However, considering the host response, tissue damage, the clinical severity and colonization of S. aureus in mammary glands, the biofilm vaccine performed better in immunogenicity and protective potential when administered by the intramammary route.     

A Newly Characterized Potentially Probiotic Strain,Lactobacillus brevis MK05, and the Toxicity Effects of its Secretory Proteins Against MCF-7 Breast Cancer Cells

Among seven strains of lactic acid bacteria (LAB) isolated from traditional dairy products, a Lactobacillus strain was identified through 16S rRNA gene sequencing and tentatively designated as Lactobacillus brevis MK05. This strain demonstrated the highest probiotic potential through biochemical analysis, including acid and bile salt resistance, as well as antibacterial activity. The collected cell-free supernatant (CFC) of L. brevis MK05 culture, compared with MRS broth with pH equal to the pH for CFC, revealed antimicrobial activity against Escherichia coli (ATCC 25922) and Staphylococcus aureus subsp. aureus (ATCC 25923), possibly due to the presence of antibacterial metabolites other than organic acids. This strain was, therefore, selected to assess the biological activity of its partially purified secretory proteins against MCF-7 cancer cells and normal fibroblast cells via the MTT assay. The partially purified cell-secreted proteins of this strain (hereafter referred to as Lb-PPSPs) showed a time and dose-dependent anti-cancer and apoptosis induction function. There was a remarkable decline in the survival rate of MCF-7 cells at doses equal to and higher than 0.5 mg/mL after 48 h. The changes in expression of the three genes involved in the apoptosis pathway (BAX, BCL-2, and BCL2L11) in MCF-7 cells treated with the Lb-PPSPs confirm its cytotoxic activity and apoptosis induction.