Single Rapid Test Detects Known and Unknown Pathogens

PCR diagnostic techniques can process no more than 50 DNA signatures at one time and the likelihood of discovering new species are low with PCR. The new technology is capable of identifying thousands of bacteria and viruses in a single test.

Scientists at the Lawrence Livermore National Laboratory (LLNL; Livermore, CA, USA) developed the LLMDA. The process begins by purifying DNA or ribonucleic acid (RNA) from a blood or stool sample. The purified DNA or RNA is labeled with a fluorescent dye, and then pipetted onto the microarray which sits on top of an incubator heated to 42 °C. The microarray contains nearly 400,000 probes arranged in a checkerboard pattern on a 2.5 × 7.5-cm glass slide. Scientists examine these probes with a fluorescent scanner and analysis software. The microarray’s checkerboard has several dozen squares for each of the thousands of organisms sequenced to date. That allows it to simultaneously examine multiple regions from each organism.

From a study that evaluated 124 wound samples from 44 soldiers injured in Iraq and Afghanistan using LLDMA, the scientists found certain bacteria, such as Pseudomonas species and Acinetobacter baumannii, which are common hospital-related infections, to be associated with wounds that did not heal successfully. Bacteria often related to the gastrointestinal system, such as Escherichia coli and Bacteroides species, were also often found in wounds that did heal successfully. The test was able to detect within 24 hours any virus or bacteria that has been sequenced and included among the array's probes.

The LLNL scientists are already building on the capacity of this microbial array. They are currently testing a next-generation LLMDA that contains 2.1 million probes representing about 178,000 sequences from 5,700 viruses and 785,000 sequences from thousands of bacteria. The new version also includes about 237,000 sequences from hundreds of fungi and about 202,000 sequences from 75 protozoa. Lawrence Livermore National Laboratory has licensed its microbial detection array technology to MOgene LC (St. Louis, MO, USA).

Related Links:
Lawrence Livermore National Laboratory
MOgene LC