This invention provides methods, systems, and compositions for detecting low abundance microbial DNA in a sample by PCR. Methods of the present invention are based on a strategy that tags the 5′-end of the target DNA templates with a non-bacterial tagging sequence so as to set the templates apart from the endogenous contaminants present in the PCR reagents. There is also provided fusion probes for tagging the templates and primer sets to amplify the tagged templates. Systems and kits for facilitating and automating methods of the present invention are also provided.
