A method for overcoming DNA degradation during PFGE for Serratia marcescens

The DNA of some bacteria is broken up by Tris-dependent endonuclease activity during the process of sample preparation for pulsed field gel electrophoresis (PFGE). Adding thiourea to the electophoresis buffer for isolates that exhibit DNA degradation has been the method used for many bacterial genera. For a particular group of isolates of Serratia marcescens this method was unsuccessful. A combination of techniques was used to overcome the problem.