title: Bacterial Suspensions Deposited on Microbiological Filter Material for Rapid Laser-Induced Breakdown Spectroscopy Identification.
abstract: Four species of bacteria, E. coli, S. epidermidis, M. smegmatis, and P. aeruginosa, were harvested from agar nutrient medium growth plates and suspended in water to create liquid specimens for the testing of a new mounting protocol. Aliquots of 30 µL were deposited on standard nitrocellulose filter paper with a mean 0.45 µm pore size to create highly flat and uniform bacterial pads. The introduction of a laser-based lens-to-sample distance measuring device and a pair of matched off-axis parabolic reflectors for light collection improved both spectral reproducibility and the signal-to-noise ratio of optical emission spectra acquired from the bacterial pads by laser-induced breakdown spectroscopy. A discriminant function analysis and a partial least squares-discriminant analysis both showed improved sensitivity and specificity compared to previous mounting techniques. The behavior of the spectra as a function of suspension concentration and filter coverage was investigated, as was the effect on chemometric cell classification of sterilization via autoclaving.
authors.affiliation: Department of Physics, University of Windsor, Windsor, Ontario, Canada.
authors.forename: Dylan J
authors.initials: DJ
authors.lastname: Malenfant
authors.affiliation: Department of Physics, University of Windsor, Windsor, Ontario, Canada.
authors.forename: Derek J
authors.initials: DJ
authors.lastname: Gillies
authors.affiliation: Department of Physics, University of Windsor, Windsor, Ontario, Canada rehse@uwindsor.ca.
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Rehse
mesh_terms: D003101:Collodion / Q000737:chemistry; D016002:Discriminant Analysis; D004867:Equipment Design; D004926:Escherichia coli / Q000737:chemistry* / Q000145:classification; D007834:Lasers; D016018:Least-Squares Analysis; D008851:Micropore Filters / Q000382:microbiology; D020102:Mycobacterium smegmatis / Q000737:chemistry* / Q000145:classification; D011550:Pseudomonas aeruginosa / Q000737:chemistry* / Q000145:classification; D015203:Reproducibility of Results; D013054:Spectrophotometry, Atomic / Q000295:instrumentation; D013212:Staphylococcus epidermidis / Q000737:chemistry* / Q000145:classification; D013535:Suspensions
chemical_list: D013535:Suspensions; D003101:Collodion
keywords: Bacterial classification; Discriminant function analysis (DFA); Laser-induced breakdown spectroscopy (LIBS); Partial least squares-discriminant analysis (PLS-DA); Pathogen identification