Date of Graduation


Document Type


Degree Name

Bachelor of Science in Agricultural, Food and Life Sciences

Degree Level



Animal Science


Zhao, Jiangchao


The prevalence of antibiotic resistant bacteria is a leading issue worldwide. Recently, there was a new law banning the use of antibiotics within the swine industry. For decades swine producers have mixed subtherapeutic amounts of antibiotics in swine feed to prevent potential infections and to increase growth rate. However, due to the constant exposure of antibiotics to these ever-evolving pathogens, the population of antibiotic resistant bacteria has increased exponentially. Currently, the swine industry is scrambling to find a suitable alternative to antibiotics that possesses antimicrobial activity and potentially promotes growth. The objective of this study was to investigate the ability of swine-origin potential probiotics to inhibit the growth of pathogenic bacteria. One hundred and thirty-five probiotic isolates, previously obtained from the swine gut microbiota, were tested against control bacteria Escherichia coli and Listeria innocua to observe their ability to inhibit both gram-negative and gram-positive bacteria. The control bacteria were inoculated into sterile, tempered agar and, after solidifying, the potential probiotics were spotted on the agar surface and left to incubate at 37°C for 20-24 h. Out of the 135 tested isolates, 121 and 134 produced signs of inhibition. These two isolates were then assessed for certain biochemical characteristics. Nutritional assays were performed where the washed cells of 121 and 134 were placed on cellulose, xylan, starch, resistant starch, lipid, and skim milk agar plates. It was observed that 121 and 134 were able to produce enzymes that digested cellulose, starch, xylan, and casein. Also, whole genome sequencing was used to identify the taxonomy and additional characteristics of 121 and 134. The results of this research support the possibility of utilizing 121 and 134 as potential probiotics that could enhance the gut health of swine.


Probiotics, Swine, Microbiome, Pathogens

Available for download on Wednesday, April 15, 2026