Genetic Mimetics of Mycobacterium tuberculosis and Methicillin-Resistant Staphylococcus aureus as Verification Standards for Molecular Diagnostics
ABSTRACTMolecular diagnostics have revolutionized the management of health care through enhanced detection of disease or infection and effective enrollment into treatment. In recognition of this, the World Health Organization approved the rollout of nucleic acid amplification technologies for identification ofMycobacterium tuberculosisusing platforms such as GeneXpert MTB/RIF, the GenoType MTBDRplusline probe assay, and, more recently, GeneXpert MTB/RIF Ultra. These assays can simultaneously detect tuberculosis infection and assess rifampin resistance. However, their widespread use in health systems requires verification and quality assurance programs. To enable development of these, we report the construction of genetically modified strains ofMycobacterium smegmatisthat mimic the profile ofMycobacterium tuberculosison both the GeneXpert MTB/RIF and the MTBDRplusline probe diagnostic tests. Using site-specific gene editing, we also created derivatives that faithfully mimic the diagnostic result of rifampin-resistantM. tuberculosis, with mutations at positions 513, 516, 526, 531, and 533 in the rifampin resistance-determining region of therpoBgene. Next, we extended this approach to other diseases and demonstrated that aStaphylococcus aureusgene sequence can be introduced intoM. smegmatisto generate a positive response for the SCCmecprobe in the GeneXpert SA Nasal Complete molecular diagnostic cartridge, designed for identification of methicillin-resistantS. aureus. These biomimetic strains are cost-effective, have low biohazard content, accurately mimic drug resistance, and can be produced with relative ease, thus illustrating their potential for widespread use as verification standards for diagnosis of a variety of diseases.