Recent advances in technology are making a major contribution in the fight against infection at healthcare facilities. Dr Ian Widger, chief technology officer at Inov8, the air disinfection company, explains.
Transmissible infections are of particular concern to the healthcare sector because of their potential to spread from one patient to another or to visitors and staff. Pathogenic organisms of particular concern include C. difficile, MRSA, E. coli, influenza and norovirus.
A broad range of tools are employed by healthcare professionals in the fight against disease. These include: hand hygiene procedures and equipment; personal protective equipment; effective cleaning regimes; sterilisation and disinfection; vaccination; patient screening; and isolation.
Most of these tools effectively address the threat posed by contamination – hands, equipment, instruments, furniture, floors etc. However, this article focuses on the role of air disinfection, a major contributor to protection against healthcare associated infections (HCAI).
Three main options exist for air disinfection. First, patients and staff can be evacuated from a room so that decontamination can take place with a high concentration of a gas such as hydrogen peroxide. This has the advantage of also treating surfaces in the room but has limited residual effect. In addition, the equipment is expensive and evacuation is not always possible or convenient.
A second option involves continuous air filtration in conjunction with a treatment technology such as ultra violet radiation. Evacuation is not required for this technique and an ongoing level of protection is provided as air is continuously removed and treated. However, effective treatment can be difficult to achieve in medium to large rooms and this solution has a limited effect on patient-to-patient or patient-to-staff transmission. Furthermore, such equipment can be noisy and costly to run.
The third and most recent innovation is continuous air disinfection with hydroxyl radicals at levels that mimic atmospheric concentrations that are harmless to humans but extremely effective against bacteria and viruses. Inov8’s Air Disinfection (AD) unit operates quietly, producing hydroxyl radicals with a very low energy requirement, providing protection against most known bacteria and viruses. A winner of the UK NHS Smart Solutions for HCAI Programme 2009, the AD unit has proved highly effective in laboratory trials and in practice at hospitals across the UK.
Trials of the AD technology began in 2006 at the Health Protection Agency's Porton Down Laboratory. Tests demonstrated a 99.999% kill of S. epidermidis and the surrogate organism MS2 Coliphage. Reflecting on the significance of this work, Professor Hugh Pennington said: “I think that it is reasonable to say that while the MS2 and influenza virus particles are very different, MS2 is very likely to be the harder virus to inactivate. So if something inactivates MS2, it is reasonable to assume that flu would not only be inactivated, but might perish faster.”
Trials at Leeds University have also shown dramatic levels of pathogen reduction in aerobiological chambers dosed with Staphylo-coccus aureus and Clostridium difficile.
Hospital trials
The infection prevention and control programme at Hereford Hospital is one example of how this technology is helping the healthcare sector. At Hereford, units were initially placed throughout the older Nightingale style wards where there had been particular problems with outbreaks and ward closures. Subsequently, units have been placed in all wards in the main hospital except for the children’s and women’s health wards.
During the first six months from April 2009, Hereford Hospital NHS Trust had no MRSA bloodstream infections and C. difficile numbers more than halved in comparison with the same time last year.
Dr Budd, medical director and director of infection prevention and control, said: “We are very pleased with these figures and think they reflect the impact of the introduction of MRSA screening of all hospital inpatients, reviewing the antibiotic prescribing policy, continued vigilance about hand hygiene, extra auditing of infection prevention practices on all our wards, and possibly the installation of Inov8 air disinfection units on nine wards.
“We are keen to maintain this progress and do even better in the future,” he added.
Dr Alison Johnson, consultant micro-biologist at Hereford, believes that it is difficult to attribute success with a particular organism to one part of the infection prevention strategy. However, she said: “We do think the Inov8 AD units are making a contribution, particularly in preventing norovirus outbreaks and ward closures.
“In 2008, there were 17 outbreaks of norovirus (nine in the older Nightingale wards and eight in the main hospital building), resulting in 144 days of ward closures. The AD units were installed in some of our older Nightingale style wards in June 2008 and then in the main hospital wards in January 2009. Since June 2008 in the Nightingale style wards, there have been three norovirus outbreaks and since January 2009 in the main hospital building, there have been no norovirus outbreaks.
Gillian Hill is the matron in infection prevention and control at Hereford Hospitals NHS Trust. While initially sceptical she is now pleased with the success of the AD units: “Norovirus represents a major challenge to hospitals – national data shows that 18 in every 100 patient admissions carry the norovirus infection and with no treatment currently available, our success in controlling the virus can only be attributed to the AD units in tandem with normal hygiene measures,” she says.
“While the symptoms of an infection usually only last for a day or two, those affected are contagious for a further 48 hours, so staff who catch the disease are required to stay at home for two days after symptoms subside. This places a heavy load on staffing and in combination with ward closures and operation delays has a major effect on the hospital. “In the absence of any opportunity to prevent norovirus outbreaks, the AD units have become the only means by which we can minimise the threat. In my view, even if the ADs had no effect on any other organisms, their role in norovirus prevention would be sufficient justification for using them.” Reducing bioburden
Royal Shrewsbury Hospital’s Renal Unit has also reported excellent results in infection prevention and the unit’s manager sister Nonny Stockdale believes that the AD has again contributed to this success.
Over the past three years, the unit has experienced a three-fold reduction in bacteraemia episodes, despite a significant rise in patient visits during this period. Stockdale oversaw the study at the Renal Unit and is delighted with the steady decrease in the number of patients experiencing infections during line insertion for haemodialysis.
The AD unit was introduced towards the end of the three-year period; however, the hospital has conducted microbiological analysis of air within the Renal Unit and results have demonstrated a significant reduction in airborne bioburden since it was installed in a clinical procedure room in May 2009.
To evaluate the effectiveness of the AD unit, air quality samples have been taken on a regular basis. Microbiological assessment has measured the number of CFUs both before and after the AD's installation. Typically, results have included Micrococcus, Penicillium and Diphtheroids.
Microbiological air quality assessments were conducted across a range of different conditions to evaluate fully the effects of the AD. These conditions included air sampling when the room was empty; when a patient was present; and with up to six staff in the room.
Stockdale says: “The decrease in bioburden once the AD unit had been installed was extremely noticeable and almost instantaneous, even when the room had many people in it, and also post-operation, when there had been a great deal of air disturbance.
“The most impressive readings resulting from the AD unit included CFU counts of 23 when the room was empty and a count of just 56 with six staff and a patient. This compares with counts without the AD unit of 174 with a patient in the room, 131 in an empty room and 72 in a newly cleaned room.
“The results without the AD unit are all significantly above the recommended rate of 35 CFU for clinical work, which proves how effective it has been in helping to improve air quality. I am therefore confident that the AD is making a significant contribution to the success of our infection prevention strategy.”
In summary, new technology offers major advantages to infection prevention and control practitioners. However, no technology should be viewed in isolation as a ‘silver bullet’. Success can be achieved only through the employment of a range of practices that complement each other and experience to-date has shown that the Inov8 AD technology is able to provide a high level of protection for patients, visitors and healthcare professionals.
