Effect of caffeic acid grafted chitosan loaded quercetin lyophilized powder formulation on avian colibacillosis and tissue distribution

Quercetin (QR), recognized as a natural antibacterial ingredient, has found widespread application in the poultry industry. This study investigated the bacteriostatic mechanism and evaluated the <i>in vivo</i> inhibitory impact of caffeic acid-grafted chitosan self-assembled micelles loaded quercetin (CA-g-CS/QR) on avian <i>Escherichia coli</i> (<i>E. coli</i>). The findings indicate that the bactericidal mechanism of CA-g-CS/QR exhibits enhanced efficacy compared to QR alone, disrupting bacterial cell walls, disassembling biofilm structures, and impeding essential components necessary for bacterial growth. Following an avian <i>E. coli</i> attack in broilers, CA-g-CS/QR demonstrated the capacity to enhance the population of beneficial bacteria while concurrently decreasing harmful bacteria within the intestinal tract. Moreover, within 3 days of oral administration of CA-g-CS/QR, a significant decrease in <i>Escherichia</i> spp. count was evident, resulting in the restoration of broilers to a healthy state. CA-g-CS/QR proved to be a significant and more efficacious solution than QR alone for avian <i>E. coli</i> disease. Furthermore, CA-g-CS/QR displayed a broader distribution range and higher concentration within the body. Ten metabolites have been identified in the liver for both QR and CA-g-CS/QR. In conclusion, CA-g-CS/QR has demonstrated a notable capacity to enhance <i>in vitro</i> and <i>in vivo</i> bacterial inhibitory effects, providing foundation for the clinical application of QR in combating avian <i>E. coli</i> infections in broilers.