Development of thermal imaging for early detection of covert cannula associated infections

Healthcare associated infections (HCAIs) are a major cause of morbidity, mortality and cost to the NHS and are the focus of a 2014 NICE quality standard entitled ’Infection prevention and control’ [1]. Clinical sepsis is the cause of 10.5% of HCAIs in England and 40.2% of HCAIs in the paediatric population, whereas bloodstream infections (BSIs) are the cause of 7.3% of HCAIs and 15.1% of HCAIs in the paediatric population [2]. BSIs can range in outcome from, resolution without treatment to clinical sepsis (a potentially life-threatening immune response triggered by an infection). Vascular access devices (i.e. cannulas) are present in the 48 hours before the onset of infection in 64% of healthcare associated BSIs [2]. Initial cannula-associated infections are detected by redness and swelling of the insertion site as well as systemic signs of infection such as an increased core temperature .

Thermal imaging is a completely safe, non-invasive technology that operates by measuring infrared emission (in the form of heat). The current devices (available to the team) can measure temperature to within 0.002 Kelvin and thus provide high sensitivity. Thermal infrared imaging has been shown to detect early infection of surgical site infections in a non-invasive manner by detecting increased blood flow caused by infection associated inflammation [3]. In collaboration with Sheffield Teaching Hospitals, we are initiating a preliminary study to investigate thermal imaging of peripheral cannulas in neonates undergoing urology surgery. Our preliminary studies involving detecting the presence of Staphylococcus aureus bacteria grown on agar, show thermal imaging can be a viable method for non-invasive detection of bacteria.

The goals of this studentship are to 1) develop thermal imaging techniques as a non-invasive means of early detection of cannula associated infections. The work will be focused on babies, as this group has the highest risk of infections caused by indwelling devices and an increased resulting morbidity and mortality. In collaboration with Sheffield Teaching Hospitals, we will carry out longitudinal studies collecting both thermal and conventional images of the site of vascular access devices. Once the device is removed (as the device is either no longer needed or if it is suspected of being infected) the presence or absence of bacteria will be determined. 2) Identification of bacterial species present within the indwelling device. The putative bacteria within the device will be enumerated, metagenomic DNA will be isolated and bacterial species identified. This will allow a more detailed understanding of the bacterial populations causing the cannula-associated infections. 3) Investigate and determine parameters for detecting bacterial growth on/in indwelling devices, this will focus on biofilm formation as more than 65% of HCAIs are caused by bacterial biofilms.