Luminescent lighting for pathogenic bacteria

Researchers at the ARC Centre of Excellence for Nanoscale BioPhotonics (CNBP) have created a fast, definitive and sensitive method for detecting pathogenic Staphylococcus aureus. Their work has been described in the journal Molecules.

Time-gated luminescent in situ hybridisation (LISH) involves the joining of a luminescent DNA probe to a specific target nucleic acid (RNA or genomic DNA) within a cell. Time-gated microscopy imaging eliminates the inherent natural fluorescence background signal usually emitted by biological samples so that the luminescence from the labelled RNA/DNA stands out with high contrast.

The approach relies on direct attachment of a single TEGylated Europium chelate to DNA that binds to intracellular rRNA and is then detected using the LISH technique. The CNBP researchers tied the probe to S. aureus and then used LISH to differentiate it from the closely related but less pathogenic Staphylococcus epidermidis.

“After short excitation, the long-lived luminescent emission from the labelled DNA probe can be detected without interference from natural background fluorescence from the biological sample,” said Dr Nima Sayyadi, Research Fellow at the Macquarie University node of the CNBP and lead author on the paper.

“This allows us to find the ‘needle in the haystack’ because only the ‘needle’ lights up. While our approach does not as yet enable drug resistance strains to be separately identified, this is subject to ongoing research.”

The ability to rapidly and accurately identify S. aureus is essential for appropriate use of antibiotics and timely intervention for infection control in patients and those at risk, including the elderly — yet the most practical approach currently for S. aureus identification in hospital first requires the culturing of cells for at least half a day to two days to provide a positive infection result in a blood specimen, followed by a series of tests which are performed and completed manually by a technician with the results usually taking a day or two. This new approach allows detection of the organism in less than 2 h.

The versatility of the approach means it can be used across multiple other diagnostic options that require the identification of intra/extracellular RNA or single-stranded DNA sequences of specific organisms or cells. Professor Jim Piper AM, Project Lead and CNBP node leader at Macquarie University, said the technique can be used to label antibodies and molecules as well as DNA, unleashing a range of applications that are central to rapid detection of infectious disease.

“CNBP is successfully undertaking highly innovative and transformational research in luminescence-based detection of single cells in human body fluid samples, and we are now seeking to further develop real-world applications to benefit the health of the community,” he said.

Image caption: Dr Nima Sayyadi, CNBP. Image courtesy of CNBP/cnbp.org.au under CC BY 2.0

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