DNA-based microarray platforms for rapid identification of bacterial species

New DNA-based microarray platforms allow rapid identification of bacterial species in cases of sepsis. Now the method has been assessed at two teaching hospital laboratories in Helsinki and London.

A total of 2,107 positive blood culture samples were examined by conventional culture methods and by a DNA-based microarray platform assay (Prove-it sepsis assay) that identifies more than 50 species of gram-positive and gram-negative bacteria. A pathogen covered by the assay was detected in 1,807 (86%) of the positive blood culture samples, and 50% of all blood cultures. Among species covered by the assay it identified 97.1% of grampositive and 96.7% of gram-negative bacteria identified by standard blood culture methods, including all 16 cultures of methicillin-resistant Staphylococcus aureus. In 341 samples bacterial species not covered by the assay were identified by blood culture, mainly Streptococcus viridans and Candida spp. Overall the sepsis assay had a sensitivity of 94.7% and a specificity of 98.8% when compared with conventional blood culture. Results of the sepsis assay were available during the same working day and, on average, 18 hours 19 minutes earlier than with the reference method. There was an increase in false negatives in polybacterial samples.

The sepsis assay was highly sensitive and specific, and faster than conventional methods. It is potentially adaptable for use in developing countries. Issues of cost will need to be addressed.

Tissari P et al. Accurate and rapid identification of bacterial species from positive blood cultures with a DNA-based microarray platform: an observational study. Lancet 2010;375:224–230; Lin S, Yang S. Molecular methods for pathogen detection in blood. Ibid:178–179 (comment).