Our lab has been investigating the use of laser-induced breakdown spectroscopy (LIBS) for the
rapid identification of bacteria in clinical specimens. The ability to rapidly identify harmful
pathogens in such specimens is crucial for initiating appropriate treatment of infectious diseases
that can kill within hours of the onset of symptoms. Current laboratory techniques can take as
long as 24-72 hours for a positive identification. Our research program is attempting to reduce
that time to minutes. Sample preparation methods utilized in our procedure include common
materials and equipment that could be easily implemented in clinical settings.
The current protocol involves the collection of bacteria using pathology swabs, centrifuging the
suspension through a custom-fabricated cone device and concentrating the bacterial cells in a
liquid suspension onto a small circular deposition area 1 mm in diameter upon a nitrocellulose
filter medium. A pulse of high-intensity laser light focused onto the circular deposition allows a
sensitive measurement of the elemental composition of the cells, leading to the detection and
identification of the bacteria. By reducing the cell concentration in various suspensions, the limit
of detection may be calculated.
Laser ablation of the filter medium and other elemental contaminants yields a non-zero
background signal when a control experiment is performed in the absence of bacterial cells. This
poster will present our efforts to identify exactly what the sources of this non-bacterial signal are,
test other types of filter media which may contribute to reduced background signal and to add
preparation steps to the protocol, which might reduce or eliminate this undesired background
signal. In addition, the investigation of how chemometric algorithms such as Partial Least
Squares Discriminant Analysis and Discriminant Function Analysis can be used to differentiate
between the LIBS emission spectra obtained from 4 different bacterial species will be discussed.