Removal of antibiotic resistance of live vaccine strain Escherichia coli MM-3 and evaluation of the immunogenicity of the new strain

Antibiotic-free selection in biotherapeutics: now and forever

The continuously improving sophistication of molecular engineering techniques gives access to novel classes of bio-therapeutics and new challenges for their production in full respect of the strengthening regulations. Among these biologic agents are DNA based vaccines or gene therapy products and to a lesser extent genetically engineered live vaccines or delivery vehicles. The use of antibiotic-based selection, frequently associated with genetic manipulation of microorganism is currently undergoing a profound metamorphosis with the implementation and diversification of alternative selection means. This short review will present examples of alternatives to antibiotic selection and their context of application to highlight their ineluctable invasion of the bio-therapeutic world.

An improved method to knock out the asd gene of Salmonella enterica serovar Pullorum

An asd-deleted (Deltaasd) mutant of Salmonella enterica serovar Pullorum (SP) was constructed using an improved method of gene knockout by combining the pi-suicide plasmid system with the Red Disruption system. The asd gene was efficiently knocked out by the recombinant suicide vector, which replaced the asd gene with the CmR gene. Based on the balanced lethal host-vector system, the phenotype of the Deltaasd mutant was further defined. The improved method was simpler and more effective than previously reported conventional methods.