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| |  New DNA Test for Various Pathogenic Bacteria Much Faster Than Current Gold-Standard System NEW YORK -- December 10, 2009 -- Identification of sepsis-causing bacteria using a new microarray platform is highly accurate and delivers results an average of 18 hours faster than the current gold-standard system, which uses techniques based on detecting inhibition of growth of bacteria through antibiotics, according to a study published online first and appearing in an upcoming edition of The Lancet. Rapid identification of bacteria commonly causing sepsis could allow species-specific therapy to be started early, leading to improved clinical outcomes. The current gold standard for detection of bacteria from patients with sepsis is blood culture, typically taking 1 to 3 days to become positive. A further 1 to 2 days might be needed for identification of bacteria and their antibiotic sensitivity patterns. To cut this additional 1 to 2 day period, new diagnostic tests that could identify bacterial species rapidly and accurately are needed. Novel DNA-based microarray platforms now allow rapid detection and species identification of several microbial pathogens. The Prove-it sepsis assay identifies more than 50 species of gram-positive and gram-negative bacteria that cause most cases of sepsis. The assay works through amplification and detection of three genes (gyrB, parE, and mecA) of these bacteria. For the study, Vanya Gant, MD, University College London Hospitals NHS Foundation Trust, University College London Windeyer Institute, London, United Kingdom, and colleagues compared the sensitivity, specificity, and time to identification of this new molecular platform with the gold standard, conventional culture-based method. In this observational study, 2107 positive blood-cultures in 3318 blood samples from patients with clinically suspected sepsis were investigated for bacterial species by both conventional culture and the Prove-it sepsis assay in 2 centres. The researchers found that 1807 of 2107 (86%) positive blood-culture samples included a pathogen covered by the assay. The assay had a clinical sensitivity of 95% and a specificity of 99%, and was 100% for both measures for methicillin-resistant Staphylococcus aureus (MRSA) bacteraemia. The assay was a mean 18 hours faster than was the conventional culture-based method, which takes an additional 1 to 2 working days. “The Prove-it sepsis assay yielded a high sensitivity and specificity, and identified bacterial species about 18 h before conventional culture methods did, providing practical and realistic delivery of same-day bacterial identification after blood-culture positivity,” the authors wrote. Clinical sensitivity and specificity of the assay were 100% for MRSA bacteraemia.” “We noted that the early knowledge provided by this new diagnostic platform could be easily integrated into everyday laboratory workflow in primary-care and secondary-care settings,” they continued. “Accordingly, we are prospectively investigating the platform’s potential contribution to clinical outcomes and management pathways, and its implementation for rapid routine diagnosis of a range of pathogens in both developed and developing countries.” In an accompanying comment, Shin Lin, MD, Stanford University School of Medicine, Stanford, California, and Samuel Yang, MD, Department of Emergency Medicine, Johns Hopkins School of Medicine, Baltimore, Maryland, said: “Will resolving these scenarios 18 h earlier than usual translate into demonstrable clinical benefit commensurate to the cost of undertaking the additional test? Although further study is needed before widespread application, the work by [Gant and colleagues] is a major advance. By combining elements of nucleic-acid and standard culture-based methods, the Prove-it sepsis assay represents an approach that encompasses the best of both worlds, bringing molecular methods to the threshold of broad pathogen detection.” SOURCE: The Lancet
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