Probing potential biomarkers in polymicrobial biofilm infections

associated with long term intra­ vascular catheters in patients requiring total parenteral nutrition

Chief Investigator	Institution	Dates	Funding Stream	Amount
Dr Nihal Bandara	University of Bristol	April 2018 to June 2021	Above and Beyond Autumn 2017	£20,000

Summary

Individuals who are unable to absorb food through their gut require nutrition to be delivered directly into their blood stream. This is done through a thin tube made from artificial material, often referred to as a 'line', that is placed in a blood vessel. Lines can be used for many years but over time become covered in a slime of germs which our immune system cannot clear. In some cases, germs break away, enter the blood and cause serious infections. However, it can take days to work out whether the infection in the blood has come from a line as the symptoms can be similar to infections initiated from other sources. As a result, patients may get unnecessary antibiotics or removal of the line. If there is a line infection, the line needs to be removed or antibiotics must be used to clear the slime. Patients have to stay in hospital up to 2 weeks to see whether the antibiotics do clear the line infection. If antibiotics fail, the infected line must be removed, and a new line needs to be placed. However, if the infection in the blood is not from a line, patients may get unnecessary antibiotics or removed the line for no reason. Therefore, we plan to design a new test using signals released by the germs to identify whether the slime in the line is the source of the infection and whether it will respond to antibiotics. This will allow clinicians to treat patients quickly and accurately to prevent harmful effects of the infection, unnecessary line replacement and antibiotics, patient discomfort, and long hospital stays.

Work to date

• From April 2018, the research team have been working on the Objective 1 in the research proposal to establish and characterize an intravascular polymicrobial biofilm.
• We have used static biofilm model to grow polymicrobial biofilms with Pseudomonas aeruginosa, Staphylococcus aureus, Staphylococcus epidermidis and Candida albicans on CVC pieces. Order of microbial introduction to the biofilm model and the duration of growth were optimized using biofilm viability (XTT) and biomass assays.
• The composition of microbes in the developed biofilms were estimated using Colony Forming Units assay (selective agar).
• Optimized biofilms were visualized in confocal laser scanning microscopy to characterize the structure and spatial orientation.
• Total parenteral nutrition was used as the biofilm growth media and optimized the concentration needed.
• Currently under discussion with University of Bristol Chemistry Department regarding small molecular analyses (potential biomarkers).
• Currently preparing catheter biofilms for scanning electron microscopy and estimating extracellular matrix components (potential biomarker).

Main findings to date

• Germs grow on 'lines' in an orderly pattern to form slimes.
• The slimes can develop on/in lines within a period of a day.
• Most common germs growing in lines do not prefer dense supply of nutrition. Rather, they require thinned nutrition supply.

Impact

The preference of thinned nutrition by the germs to develop slimes on lines indicate that inadequate rinsing of lines after delivering nutrition can lead to slime formation. Therefore, it is important to inform patients the value of proper rinsing of lines after nutrition delivery.

Other project outcomes

Academic collaboration with School of Chemistry (small molecular analyses).

Wolfson Bioimaging Facility (Biofilm imaging).

Updated October 2019