Molecular Device Identifies Bacterial Pathogens

Novel DNA-based microarray platforms enable rapid detection and species identification of many pathogens, including bacteria.

The assay is a novel polymerase chain reaction (PCR) and microarray method that is based on amplification and detection of the genes for gyrase subunit B (gyrB), DNA topoisomerase IV, subunit B (parE), and Methicillin resistance (mecA) of 50 bacterial species.

The molecular device, known as the Prove-it sepsis assay, was tested in the Helsinki University Hospital, (Helsinki, Finland). Blood samples from patients with clinically suspected sepsis were investigated for bacterial species by both conventional culture and Prove-it sepsis assay (Mobidiag; Helsinki, Finland) in two centers in the UK and Finland). In this method, DNA was extracted from a 0.5 mL sample of blood-culture material by use of an automated platform, and proprietary gene regions of topoisomerase genes and the mecA gene were amplified by PCR. The PCR amplicons were subsequently overlaid onto the Prove-it tube microarray in which hybridization was detected in one reaction and final bacterial identification was by solid-state hardware. The scientists assessed the sensitivity, specificity, and turnaround time of the sepsis assay.

Of the 3,318 blood samples from patients with clinically suspected sepsis, 2,107 had positive blood-culture samples. Of these, 1,807 (86%) had positive blood-culture samples that included a pathogen covered by the assay. The assay had a clinical sensitivity of 94.7% and a specificity of 98.8%, and 100% for both measures for methicillin-resistant Staphylococcus aureus bacteremia. The assay was on average 18 hours faster than the conventional culture-based method, which takes an additional one to two working days.

The definitive identification of bacterial species with this microarray platform was highly sensitive, specific, and faster than was the gold-standard culture-based method. This assay could enable fast and earlier evidence-based management for clinical sepsis. The results of the study were published on January 16, 2010, in the Lancet.

Related Links:
Helsinki University Hospital
Mobidiag