The present invention relates generally to the field of detection of microorganisms, in particular detection of bacteria, to methods for measuring enzyme activity, such as DNA polymerase activity, and particularly relates to such methods performed on microbial crude lysates, useful for determining microbial enzyme activities which can be linked to amplification signal generators such as real-time Polymerase Chain Reaction (PCR) techniques, thereby enabling determination of microbial pathogens in samples such as unpurified blood and other body fluids. This invention also relates to reagents for use in such methods, and to test kits comprising such reagents for carrying out the methods.