Effect of Antibiotics on the Colonization of Live Attenuated Enteritidis Vaccine in Chickens.

Salmonellosis, caused by Enteritidis, is a prevalent zoonosis that has serious consequences for human health and the development of the poultry sector. The Enteritis live vaccine (Sm24/Rif12/Ssq strain) is used to prevent Enteritidis around the world. However, in some parts of the world, poultry flocks are frequently raised under intensive conditions, with significant amounts of antimicrobials to prevent and treat disease and to promote growth. To investigate whether antibiotic use influences the colonization of orally administered live vaccines, 240 1-day-old specific pathogen-free chicks were randomly divided into 24 groups of 10 animals for this study. The different groups were treated with different antibiotics, which included ceftiofur, amoxicillin, enrofloxacin, and lincomycin-spectinomycin. Each group was immunized 2, 3, 4, and 5 days after withdrawal, respectively. At 5 days after immunization, the blood, liver, and ceca with contents were collected for the isolation of the live vaccine strain. The result showed that no vaccine strain was isolated in the blood and liver of the chicks in those groups. The highest number of vaccine strains was isolated in the cecum from chicks vaccinated 2 days after ceftiofur withdrawal, and no vaccine strain was isolated from the cecum in chicks immunized 3 days after ceftiofur withdrawal. Among the chickens immunized 4 days after the withdrawal of amoxicillin, enrofloxacin, and lincomycin-spectinomycin, the number of vaccine colonization in the cecum was the highest, which was higher than that of the chickens immunized at other withdrawal interval (2, 3, and 5 days) groups and was higher than that of the chickens without treatment ( < 0.05). This study provides a reference for the effective use of the Enteritidis live vaccine and key antibiotics commonly utilized in the poultry industry.