Brussels, 30 Sep 2005
British scientists have developed an electronic nose that can test for superbug MRSA infections in just 15 minutes.
Standard culture tests to identify MRSA (methicillin-resistant Staphylococcus aureus) take two or three days, preventing a rapid management of outbreaks as infected patients remain untreated and at risk of infecting others. With adequate funding, the authors think the e-nose could be used in all hospitals within a year or two.
The researchers responsible for the discovery, presented in the journal Sensors and Actuators B, report that the electronic nose can recognise the specific mixture of volatile organic compounds that S. aureus strains excrete.
The idea of sniffing out superbugs came to David Morgan, a surgeon at the Heart of England Hospital, Birmingham, while operating on neck abscesses on two different patients and noticing that their infections had slightly different smells. Dr Morgan wondered if 'a machine could work out what the bacterial infections were from the smell alone', reports New Scientist.
The electronic nose, a device long used for safety and quality control in the food, wine and perfume industries, has already been developed to sniff out other infections and cancers. Known as the Cyranose, the electronic nose uses biosensor technology to produce a 'smellprint' of the volatile organic compounds that comprise human breath and other scents. Neural network software built into the e-nose can learn to recognise these specific smellprints.
Dr Morgan approached Warwick University engineer Ritaban Dutta and his colleagues to develop the idea of training an electronic nose to recognise the smell-prints of MRSA. They first trained an e-nose to recognise the smell-prints of MRSA and the related but more easily treated MSSA (methicillin susceptible S. aureus) by exposing them to nasal swabs from people carrying the infection. They then put their e-nose to the test using swabs from 150 patients whose infection status was already known from culture tests. The system correctly detected 96 per cent of those who had an S. aureus infection.
The e-nose developed by the team can sit on a doctor's desk and analyse gasses expelled by swabs from patients for signs of MRSA and other strains of S. aureus, obtaining results within minutes, which is important for hospital screening and isolating infected patients to prevent disease outbreaks. The current way of analysing ear, nose and throat swabs involves sending samples off to the lab and waiting 72 hours for a result. DNA-based tests are being trialled to reduce test times to two hours. The estimated cost of the E-nose is 88,000 euro.
The only drawback is that the e-nose system cannot yet distinguish the methicillin-resistant superbug from the methicillin-susceptible strain. But even if researchers do not succeed into training it to do so, Dr Morgan suggests that this e-nose could be used as a quick screening system to decide which patients or healthcare workers should be given the two-hour DNA-based test, which can spot the difference between MSSA and MRSA.
Staphylococcus Aureus, or Staph, are bacteria commonly carried on the skin or in the nose of healthy people, and humankind have been living with this bug for many generations without many problems. But now some strains of Staph have become resistant to antibiotics frequently used to treat Staph infections, such as Methicillin, and thus are now called Methicillin Resistant Staphylococcus Aureus or MRSA.
Staph infections, including MRSA, occur most frequently among persons in hospitals, and healthcare facilities who have weakened immune systems. MRSA superbug is the chief reason of hospital infections around the world. For patients, there is a risk of developing a serious infection due to MRSA, or of having to wait for urgent treatment while they are first tested to see whether they are carriers. The worldwide cost of MRSA infection is estimated at over 30 billion euro per year.
According to research from the UK's Universities of Bath and Bristol and Southmead Hospital in Bristol, published in May 2004, MRSA bacteria that are increasingly resistant to vancomycin, the antibiotic of last resort in the war against superbugs, have emerged independently in at least eight countries: the UK, the US, France, Japan, Sweden, Poland, Norway and China.
The October issue of the Lancet Infectious Diseases has recently published the conclusions of a group experts who conclude that MRSA is everybody's business, not only that of hospital epidemiologists and a few opinion leaders. Despite extensive research, 'uncertainty remains about the best approach to prevent and control this worldwide plague. [...]The situation with MRSA might become comparable to that observed for other infectious problems such as severe acute respiratory syndrome and mad cow disease - economic and political pressure may contribute to compliance and uniformity in control measures and to allocation of resources to improve patients' safety,' they conclude. To download the abstract of the journal Sensors and Actuators B paper, please click here Remarks: Reference documents: Ritaban Dutta, David Morgan, Nicky Baker, Julian W. Gardner and Evor L. Hines. Identification of Staphylococcus aureus infections in hospital environment: electronic nose based approach. Sensors and Actuators B: Chemical, Volume 109, Issue 2, 14 September 2005, Pages 355-362 Meticillin-resistant Staphylococcus aureus; The Lancet Infectious Diseases, Volume 5, Issue 10, October 2005, pp. 653-663