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Applied Optics

Applied Optics

APPLICATIONS-CENTERED RESEARCH IN OPTICS

  • Editor: Joseph N. Mait
  • Vol. 51, Iss. 7 — Mar. 1, 2012
  • pp: B99–B107

Pathogen identification with laser-induced breakdown spectroscopy: the effect of bacterial and biofluid specimen contamination

Qassem I. Mohaidat, Khadija Sheikh, Sunil Palchaudhuri, and Steven J. Rehse  »View Author Affiliations


Applied Optics, Vol. 51, Issue 7, pp. B99-B107 (2012)
http://dx.doi.org/10.1364/AO.51.000B99


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Abstract

In this paper, the potential use of laser-induced breakdown spectroscopy (LIBS) for the rapid discrimination and identification of bacterial pathogens in realistic clinical specimens is investigated. Specifically, the common problem of sample contamination was studied by creating mixed samples to investigate the effect that the presence of a second contaminant bacterium in the specimen had on the LIBS-based identification of the primary pathogen. Two closely related bacterial specimens, Escherichia coli strain ATCC 25922 and Enterobacter cloacae strain ATCC 13047, were mixed together in mixing fractions of 101, 1001, and 10001. LIBS spectra from the three mixtures were reliably classified as the correct E. coli strain with 98.5% accuracy when all the mixtures were withheld from the training model and classified against spectra from pure specimens. To simulate a rapid test for the presence of urinary tract infection pathogens, LIBS spectra were obtained from specimens of Staphylococcus epidermidis obtained from distilled water and sterile urine. LIBS spectra from the urine-harvested bacteria were classified as S. epidermidis with 100% accuracy when classified using a model containing only spectra from other Staphylococci species and with 88.5% accuracy when a model containing five genera of bacteria was utilized. Bacterial specimens comprising five different genera and 13 classifiable taxonomic groups of species and strains were compiled in a library that was tested using external validation techniques. The importance of utilizing external validation techniques where the library is tested with data withheld from all previous testing and training of the model was revealed by comparing the results against “leave-one-out” cross-validation results. Last, the effect of using sequential models for the classification of a single unknown spectrum was investigated by comparing the misclassification of two closely related bacteria, E. coli and E. cloacae, when the classification was first performed using the five-genus bacterial library and then with a smaller model consisting only of E. coli and E. cloacae specimens. This result shows the utility of using successively more targeted analyses and models that use preliminary classifications from more general models as input.

© 2012 Optical Society of America

OCIS Codes
(140.3440) Lasers and laser optics : Laser-induced breakdown
(170.4580) Medical optics and biotechnology : Optical diagnostics for medicine
(300.6210) Spectroscopy : Spectroscopy, atomic
(280.1415) Remote sensing and sensors : Biological sensing and sensors
(300.6365) Spectroscopy : Spectroscopy, laser induced breakdown

History
Original Manuscript: September 23, 2011
Revised Manuscript: December 20, 2011
Manuscript Accepted: December 26, 2011
Published: February 24, 2012

Virtual Issues
Vol. 7, Iss. 5 Virtual Journal for Biomedical Optics

Citation
Qassem I. Mohaidat, Khadija Sheikh, Sunil Palchaudhuri, and Steven J. Rehse, "Pathogen identification with laser-induced breakdown spectroscopy: the effect of bacterial and biofluid specimen contamination," Appl. Opt. 51, B99-B107 (2012)
http://www.opticsinfobase.org/ao/abstract.cfm?URI=ao-51-7-B99

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