Gram positive bacterial mutants and methods of generating and using such mutants

The present invention concerns gram positive bacterial mutants, particularly staphylococcus mutants of the Newman strain. It also involves transposable elements that can be used to generate these mutants, as well as methods of creating such mutants with these elements. The inventions also includes methods of using the bacterial mutants to screen for different types of genes, including virulence genes, which can lead to assays for drug compounds useful in the treatment of bacterial infection.