The present invention provides cells having more than two drug resistance genes and at least two different resistance genes that have been recombined into the chromosome of a cell. It also teaches the processes for preparing cells by recombining two or more different drug resistance genes into the chromosome of a cell. The invention further shows a screening method using the cells of described herein that may be used to accomplish high throughput screening of, among other things, natural products and/or whole cells isolated from the environment.