Design of a single-tube, endpoint, linear-after-the-exponential-PCR assay for 17 pathogens associated with sepsis



Lawrence J. Wangh, Department of Biology, Brandeis University, Waltham, MA 02453-2728, USA. E-mail:



The goal of this study was to construct a single-tube multiplex molecular diagnostic assay using linear-after-the-exponential (LATE)-PCR for the detection of 17 microbial pathogens commonly associated with septicaemia.

Methods and Results

The assay described here detects 17 pathogens associated with sepsis via amplification and analysis of gene-specific sequences. The pathogens and their targeted genes were: Klebsiella spp. (phoE); Acinetobacter baumannii (gyrB); Staphylococcus aureus (spa); Enterobacter spp. (thdF); Pseudomonas aeruginosa (toxA); coagulase-negative staphylococci (tuf), Enterococcus spp. (tuf); Candida spp. (P450). A sequence from an unidentified gene in Lactococcus lactis, served as a positive control for assay function. LATE-PCR was used to generate single-stranded amplicons that were analysed at endpoint over a wide range of temperatures in four fluorescent colours. Each target was detected by its pattern of hybridization to a sequence-specific low-temperature fluorescent probe derived from molecular beacons.


All 17 microbial targets were detected in samples containing low numbers of pathogen genomes in the presence of high levels of human genomic DNA.

Significance and Impact of the Study

This assay used new technology to achieve an advance in the field of molecular diagnostics: a single-tube assay for detection of pathogens commonly responsible for septicaemia.