The present invention is directed to methods for confirming the identity of an item or product using a segment of DNA present in a killed microorganism as a tag. In some embodiments, a food compatible microorganism containing a target nucleotide sequences not present in the item to be tagged is selected to serve as a tag and an identity unique identifier and/or other metadata for of the item is then saved for that tag in a database. The microorganism is killed to create a tag with the target nucleotide sequence and the tag is added to the item. The identity of the item can later be confirmed by extracting the DNA in the item and amplifying the target nucleotide sequence or sequences using PCR techniques, sequencing each amplified target nucleotide sequence; and then comparing them to the nucleotide sequence saved for the target nucleotide sequence.