Drug-resistant tuberculosis (TB) often arises from single nucleotide mutations in the bacterial genome. Currently, the conventional approach for detecting antibiotic resistance requires prolonged cultivation of bacteria under strictly controlled conditions. This is a well-established yet laborious procedure that often impairs early treatment. Therefore, the need for rapid molecular tests is constantly increasing, especially in high TB burden countries worldwide.
EMPE Diagnostics tests combine the molecular padlock probe  with the lateral flow biosensor to detect the presence of pathogens and to identify antibiotic resistance in a fast and accurate manner. Padlock probes are highly selective DNA probes that can be circularized when bound to a specific region of DNA. They enable specific and multiplex detection of single nucleotide variations.
EMPE Diagnostics probe panels are engineered to detect the specific sequences that correlate to resistance or susceptibility to various antibiotics in pathogen DNA amplified by PCR. The ability of padlock probes to accurately and specifically identify DNA sequences is backed up by a strong scientific foundation reflected in hundreds of peer-reviewed publications in high impact journals such as Science, Nature Genetics, Nature Biotechnology, Nature Methods and PNAS among others.
To visualize a successful DNA detection event, the circularized padlock probes are replicated through a process called Rolling Circle Amplification, RCA. The phi29 DNA polymerase is employed to make DNA polymers, containing hundreds of identical repeats of the original padlock probe. The polymer is cleaved into individual units – monomer – that are finally detected on the EMPE Diagnostics lateral flow cassette . Depending on the antibiotic resistance profile of the bacteria, distinctive types of these monomers are generated.
Our biosensing devices are engineered around two principal objectives: accuracy and user friendliness. The MDR-TB Assembled Cassette encapsulates a nitrocellulose membrane strip with multiple detection zones. When an assay product is applied onto the cassette port, the monomers flow along the membrane driven by capillary forces. They selectively attach to their respective zones, producing a visible pattern reflecting the antibiotic resistance profile of the bacteria. Labels along the sample preview window make the interpretation of the test result easy.
Our first product to be launched, mfloDx™ MDR-TB, can detect the Mycobacterium tuberculosis complex, mutations in the rpoB gene, causing rifampicin resistance, and mutations in the katG and the inhA genes, causing resistance to isoniazid. The detection of these mutations is visualized as clear bands on the lateral flow cassette, while absence of mutations is confirmed by instead showing bands corresponding to the wild type genotype at these positions.
 Nilsson, M. et al. (1994). Padlock probes: circularizing oligonucleotides for localized DNA detection. Science 265 (5181), 2085–2088.
 Pavankumar AR. et al. (2016). Proficient Detection of Multi-Drug-Resistant Mycobacterium tuberculosis by Padlock Probes and Lateral Flow Nucleic Acid Biosensors. ACS Anal. Chem, 88(8):4277-84.