Research and Development Projects
The NBL is currently working on a number of research projects, some within the NBS and others trialing new developments by Biomedical companies. NBL has been involved in work to improve blood and tissue safety. NBL validated the Diversion procedure as a efficient method to prevent bacterial contamination of donations from the donor’s arm. NBL has also tested the efficacy of using Peracetic acid as an alternative method of decontaminating tissues
- Antibiotic Cocktail Validation
- Pulse Field Gel Electrophoresis
- A real-time PCR assay to detect Eubacterial 16s rDNA in platelets
- Molecular identification system for the NBL
- Bacterial Detection Systems
A variety of antibiotic cocktails are used in different ways to decontaminate tissues in the tissue banks across the country. The NBL has currently recommended the 'best practice' cocktail which has optimum performance at 37°C for heart valve decontamination. Experiments are also underway to evaluate the antibiotic cocktail on porcine and human heart valve tissues and to remove or neutralise the residual antibiotic from the tissue samples.
Pulse Field Gel Electrophoresis (PFGE) is a molecular typing method used to compare epidemiologically related isolates.
In this method unsheared bacterial DNA prepared in agarose blocks is cut using rare cutting restriction endonucleases to produce, optimally, 20 – 40 fragments. These fragments are then separated through an agarose gel using a current ”pulsed” in different directions over a gradient of time intervals allowing the fragments to be resolved. Banding patterns may be interpreted by eye or with the aid of Bionumerics software to assess the interrelationship of the isolates.
Bacterial contamination of platelet concentrates (PC's) is a major cause of transfusion - related morbidity and mortality. The use of a real-time PCR assay to detect Eubacterial 16s rDNA in platelets is a potential tool for bacterial screening of PC's prior to transfusion. Currently work is being done in collaboration with Great Ormond Street Hospital to evaluate the assay. The efficiency of a range of different DNA extraction methods, suitable primer sets and probes and the sensitivity of the assay are being assessed.
Traditional microbial detection and identification methods are based on phenotypic properties, such as ability to grow on certain carbon sources or catalyse the conversion of specific substrates. Molecular diagnosis, such as PCR or DNA sequencing now provides greater discrimination and precision to rapidly detect and identify multiple pathogens. The current project envisages the application of gene sequence information, which is available in public databases, and multiplex PCR to construct a microarray for identification of bacteria
Currently, identification of Staphylococcus spp. by molecular means is being undertaken by PCR and sequencing of the recA and rpoB genes. Signature probes immobilised on a microarray platform will then selectively bind to their respective species and provide the identification of the test Staphylococcus spp. strain. Once the system is fully functional for Staphylococcus spp. identification, similar technology will be used to identify a further range of bacteria, including Acinetobacter spp. and Pseudomonas spp. This work is in collaboration with the Health Protection Agency.
The NBL has evaluated other systems of detecting bacterial contamination of blood products such as PALL eBDS, Hemosystem Scansytem and Versatrek. Currently NBL is evaluating Bac-Detect, which utilises dielectrophoresis. It combines advanced microelectronic and microfluidic technologies to detect the presence of bacteria in platelets.