Porcine post-weaning diarrhea (PWD) continues causing substantial economic loss to swine producers. Vaccines strategy especially live attenuated vaccines could be the most effective and most affordable treatment against PWD. However, development of live attenuated vaccines typically needs antibiotic selection system (by using antibiotic resistance genes for selection). Release of large quantity of live vaccine strains carry antibiotic resistance genes could transfer antibiotic resistance genes to microorganisms in the environment. That causes major concerns on environment and medical practices using antibiotic drugs. In this study, we developed a non-antibiotic selection vector that can be used to express antigens against PWD. The experimental vaccine strains are selected by this non-antibiotic system, thus, we resolve problems regarding release of antibiotic resistance genes to the field. We used this vector to express enterotoxin antigens from enterotoxigenic Escherichia coli (ETEC), and to develop a live attenuated vaccine against PWD. For detailed information, please contact Dr. Weiping Zhang at 605-688-4317 or e-mail at [email protected].