Patent ID: 7098042

Claim:
A method for calibrating or determining accuracy or efficiency of a microbial assay, comprising: (a) providing an internal quality control standard to a sample to be assayed and suspected of containing a microorganism type, the standard comprising a defined quantum of a modified form of the microorganism type, wherein the modified microorganism comprises a detectable tag such that the modified microorganism can be differentiated from the corresponding unmodified microorganism in a sample being assayed; (b) carrying out an assay on the sample so as to detect and determine the number of unmodified microorganisms and the number of modified microorganisms present in the sample; and (c) comparing the number of modified microorganisms detected by the assay with the defined quantum of modified microorganisms provided to the sample so as to calibrate or determine the efficiency of the assay, wherein the number of detected modified microorganisms is compared with the defined quantum of modified microorganism added to the sample and the comparison is indicative of the efficiency of the assay for the microorganism.