the present invention relates to novel methods , and kits , for selectively excluding dead cells from a mixture containing live and dead cells , such as microbe cells in clinical samples , blood products , medical / biotechnology products and food products where subsequent interrogation of the selected live cells are an indicator of the presence of microbe viability . in particular , the invention relates to improved methods for performing direct nucleic acid amplification techniques such as polymerase chain reaction and isothermal techniques in blood and other body fluids , for correlation with microbe cell viability from bacteremia and fungemia samples . the improved methods provided by the invention are particularly advantageous for the diagnosis of septicemia and to determine pathological conditions in all other normally sterile body fluids .