Purpose: The purpose of this study was to evaluate antimicrobial activity of CN in fluids from animals with metritis and mastitis.
Methods: CN was prepared by cross-linking of chitosan solution, and the size of CN was measured by nanoparticle analyzer. For antimicrobial activity of CN, cow uterine fluids and milk samples were collected from animals with metritis and subclinical mastitis, respectively. Antimicrobial activity of CN was evaluated by the enumeration of naturally infected pathogens in the fluids.
Results: CN treatment effectively reduced the concentrations of pathogens in the matrices of cow uterus and milk. The antimicrobial activity varied depending on matrices and CN concentrations. In LB broth, 0.1% CN completely killed E. coli O157:H7 during 2 h of incubation. In milk, naturally infected pathogens were completely killed in 4 h with 0.1% CN. In cow uterine fluid, although the growth of naturally infected pathogens was inhibited at 0.1%, higher concentration (0.6%) of CN was required to kill pathogens, suggesting the antimicrobial activity of CN is inhibited in the uterine fluid. In addition, CN resistance was not detected in E. coli O157:H7 after treatment, suggesting CN provides insight for potential use for antimicrobial resistant microorganisms.
Significance: The data demonstrate that a natural antimicrobial agent CN retains antimicrobial activity in different matrices that provides encouraging solution to enhance animal and public health, especially targeting antimicrobial resistant microorganisms.