In vivo Evaluation of Antimicrobial Activity of Chitosan Microparticles in Cows with Uterine Disease

Introduction: Antibiotic drugs have been key elements to sustain human and animal health. However, the essential role of antibiotics has been challenged by the occurrence of antimicrobial resistance (AR). The rise of AR is a tremendous concern for public and animal health and problems of AR are growing mainly because new antibiotic development is not keeping pace with the emergence of AR. Chitosan microparticles (CMs) have been developed as a natural antimicrobial agent, and in vitro results provide promising use for disease treatment. 

Purpose: The purpose of this study was to evaluate in vivo antimicrobial activity of CMs in an animal model, cow uterus with uterine disease.

Methods: For in vivo animal experiments, Holstein cows with metritis (n = 30) were randomly assigned to one of three treatments as they were diagnosed with metritis: CMs treatment, Ceftiofur antibiotic treatment, and no treatment. To evaluate the efficacy of CMs, we enumerated intrauterine pathogenic Escherichia coli (IUPEC) in uterus. Uterine swab samples were daily collected for 7 days and enumerated using CHROMagar E. coli.

Results: CMs treatment effectively reduced the shedding of IUPEC in the cow uterus. The efficacy of antimicrobial activity was better than ceftiofur in the reduction of this pathogen. Cows treated with CMs stopped the shedding of IUPEC within five days of treatment, while 50% of ceftiofur treated cows shed for more than seven days. In addition, CMs did not trigger bacteriophage induction and Shiga toxin overexpression in E. coli O157:H7, suggesting that CMs may provide insight to treat infections caused by pathogens encoding toxin genes in the phage genome. 

Significance: The data demonstrate that a natural antimicrobial agent CMs retains antimicrobial activity in cow uterus with uterine disease that provides encouraging solution to enhance animal and public health, especially targeting antimicrobial resistant microorganisms.