Date of Award

12-19-2018

Publication Type

Master Thesis

Degree Name

M.Sc.

Department

Physics

Supervisor

Steven J Rehse

Rights

info:eu-repo/semantics/openAccess

Abstract

A rapid elemental analysis technique known as laser-induced breakdown spectroscopy (LIBS) has been shown to be a promising tool for detection and identification of pathogens. The aim of this work was to demonstrate the feasibility of the LIBS technique as a point-of-care diagnostic tool for bacterial infection. A size-based technique for separating bacteria from unwanted material that could be present in a clinical specimen was developed using a custom-built centrifuge tube insert device. Tungsten powder was used to simulate unwanted contaminants in a bacterial suspension, all of which was removed from suspension while 90% of the bacteria were successfully separated from the contaminant. A new bacterial mounting procedure was developed by designing and constructing a small aluminum cone for use with the centrifuge tube insert. The bacterial limit of detection for this new mounting procedure was calculated to be 5000 CFU per laser shot location – an order of magnitude improvement from previous mounting procedures. Methods to reduce the measured shot-to-shot variation assumed to be caused by uneven deposition of the bacteria using either the detergent Tween 20 or growth of bacteria in a liquid culture medium were investigated. No significant effect was observed. The ability to detect bacteria that were collected using common pathology swabs to more closely simulate the collection of some clinical specimens was also investigated. The efficiency of bacterial cell pick-up with a swab and subsequent shake-off prior to LIBS testing was determined. Protocols for collecting bacteria from swabs were developed and a study of the resulting LIBS emission as a function of bacterial coverage was conducted using the new mounting procedure.

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