Biofilm formation monitoring in real time on coated medical devices

A research team leaded by Morgan R. Alexander from School of Pharmacy, University Park, Nottingham  conducted a study where they explain the attachment of bacteria to medical devices in a real time. Their study was able to detect the early biofilm formation before the infection occur. They uses an optical fiber sensor (long period grating (LPG) ) which was in combination with lumen of endotracheal tubes (ETTs) for real time monitoring of  bacteria Pseudomonas aeruginosa surface colonization and biofilm formation. 

These results are publish in Royal Society of Chemistry under title "Real time monitoring of biofilm formation on coated medical devices for the reduction and interception of bacterial infections".

Yasin Kurmoo, the first author of this research paper explain that they observe a reproducible exponential relationship between the biomass and optical signal which allow the quantitative measure of biomass by the optical sensor.

A shift in wavelength of LPG attenuation band for 24 hours. they compare it with biofilm amount with the help of  a confocal fluorescence microscope. A low amount of almost 81µg/cm2 of biofilm was detected by LPG sensor as compared to quantification with confocal imaging. Change in the refractive index was likely to be the reason  of this linear increase in wavelength shift for the attenuation at the surface of the bio-sensor.

The author explain, For device-centered infections, bacterial attachment and subsequent biofilm formation on medical device surfaces is a prerequisite. Biofilms are bacterial cell aggregates, encased in a slime sheet, incorporating polymeric extracellular substances (EPS). EPS, which is formed by bacteria, contains exopolysaccharides, extracellular DNA, proteins and other components that protect the environment and limit the cellular access to antimicrobials. Bacteria within biofilms are up to 1000 times more resistant than planktonic cells to antimicrobials and the host immune system and are able to establish antimicrobial resistance by swapping genes for resistance.

As a five-step process, the general biofilm life cycle for pathogens such as Pseudomonas aeruginosa has been identified. In patients with indwelling implants, pathogenic bacteria undergoing this life cycle on medical device surfaces pose a serious risk of infection.

Biofilm formation of  P. aeruginosa can cause  device associated infection. They compare the biofilm formation from artificial sputum or minimal growth medium (RPMI-1640) on optical fibers and uncoated ETTs alongside with acrylate polymer which is biofilm resistant.

Architectural variations between the biofilms cultivated in the two media and between the uncoated and coated samples were demonstrated by the confocal fluorescence images. On the uncoated RPMI-1640 sample (at 37 C), P. aeruginosa biofilm was uniform, flat biofilms formed, whereas patchy areas of biomass were observed on the coated sample and in ASM (at 37 °C and room temperature). This is not uncommon, as the development of biofilms also starts by densely colonising substratum areas. This provides some insights into the differences between growth media, whereby different environments for biofilm formation have been created by the nutrient composition.

The team further concluded that, to maximize the chance of biofilm detecting the better positioning of the sensor is required. In earlier study it was observed that heavy biofilm formation was occur at the luminal surface of ETT.