Spectral identification of hospital acquired infections demonstrated

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Scientists at Applied Research Associates in the US have used intensified CCD cameras to analyse Laser Induced Breakdown Spectroscopy (LIBS) data to differentiate between strains of a multiple-antibiotic-resistant species.

Dr Rosalie Multari and her colleagues at Applied Research Associates believe that the ability to distinguish both species and strains using only raw spectra raises the prospect of rapid diagnostic instrumentation for use both within laboratories and in the field.

At a time of rising levels of MRSA and other hospital acquired infections, LIBS has been demonstrated to be a rapid and reliable technique for detection of life-threatening bacterial pathogen species that can be found in medical environments.

Dr Multari's team used the Andor iStar intensified CCD camera to analyse ten accumulated spectra from the laser-induced plasma plumes, with each spectrum accurately delayed by 1μs from the laser pulse and integrated on a 20μs temporal scale. The overall 1 second detection period allowed the identification of the five bacterial samples with 100 per cent accuracy, including Escherichia coli, three methicillin-resistant Staphylococus aureus (MRSA) strains and an unrelated MRSA strain.

'Andor iStar Intensified CCD is the perfect platform for such challenging LIBS measurements,' commented Andrew Dennis, director of product management at Andor. 'Coupled with Echelle-based spectrographs, the iStar allows access to the highest bandwidth coverage while simultaneously achieving the highest spectral resolution and highest time-resolution.'

The LIBS team at Applied Research Associates is also investigating its use in industrial process monitoring, environmental monitoring and workplace surveillance for harmful materials, as well as deployment in space exploration. Unlike other atomic spectroscopy techniques, LIBS does not require intensive sample preparation and lends itself to automated or unattended situations outside of the controlled laboratory environment.

The LIBS technique directs a focused laser pulse onto a target, which may be a solid, liquid, or a gas. The energy from the pulse vaporises, atomises and ionises the target material to form a micro-plasma, which emits light as a result of relaxation of electrons from excited to lower energy states. Typically, this light is routed to an Echelle spectrograph and the spectral signature of the plasma is uniquely characteristic of the elements within the target.

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