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Efficacy of polyhexamethylene biguanide nanoparticles to control Mastitis-causing Staphylococcus aureus

Grant number: 19/01705-4
Support Opportunities:Scholarships in Brazil - Doctorate
Effective date (Start): June 01, 2020
Effective date (End): February 28, 2022
Field of knowledge:Agronomical Sciences - Veterinary Medicine - Preventive Veterinary Medicine
Principal Investigator:Marcos Veiga dos Santos
Grantee:Renata de Freitas Leite
Host Institution: Faculdade de Medicina Veterinária e Zootecnia (FMVZ). Universidade de São Paulo (USP). São Paulo , SP, Brazil


Post-milking teat disinfection is a common practice to prevent contagious Mastitis pathogens as Staphylococcus aureus in dairy herds. Previous studies reported the in vitro antimicrobial activity of the polyhexamethylene biguanide (PHMB) polymer against Staphylococcus aureus isolated from Bovine Mastitis cases. The hypothesis of the present study is that Mastitis-causing Staph. aureus produce biofilm and invade mammary gland epithelial cells, and that nanoparticles constituted by PHMB polymer inhibit Staph growth. aureus and present rapid onset and long duration of antimicrobial activity, after application on teat surfaces. Thus, 10 Staph. aureus strains obtained from clinical and subclinical Mastitis and resistant to antimicrobials will be used in the present study. Firstly, these strains will be evaluated regarding their biofilm-forming ability and host cellular invasion by crystal violate staining technique and by intracellular infections of Mac-T cells, respectively. Then, nanoparticles antimicrobial activity will be evaluated against Staph. aureus strains by: a) agar disk diffusion assay where filter paper disks will be impregnated with PHMB nanoparticles and with active compounds present in comercial teat disinfection solutions and the diameters of the zones of inhibition will be measured in the disk diffusion assay; b) excised teat protocol where teats will be dipped in a bacterial challenge solution and disinfected by antimicrobials; then, Colony Forming Units (CFU) will be counted. Thus, it is expected to evaluate the antimicrobial activity of PHMB against Mastitis-causing Staph. aureus and PHMB nanoparticles efficacy in excised teats for its usage as a tool to control Mastitis in dairy herds. (AU)

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