LIBS technique detects and identifies harmful bacteria

For the first time, scientists have used a chemometric analysis of LIBS data in a blind test to successfully identify five pathogenic bacterial samples and differentiate between strains of a multiple-antibiotic-resistant species.

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. The spectral signature of the plasma is uniquely characteristic of the elements within the target.

Dr Rosalie Multari and her colleagues at Applied Research Associates in the US believe that the ability to distinguish both species and strains using only raw spectra raises the prospect that rapid diagnostic instrumentation based on the technique could be used within laboratories and in the field.

Dr Multari’s team used an 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 one-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.

The 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 a controlled laboratory environment.