Laser induced fluorescence (LIF) based detection and discrimination of bacteria from oils, pollen, and chemicals

Abstract

When pathogenic bacteria are brought out accidently or on purpose fast detection is important to avoid spreading of bacteria through infected people. The laser induced fluorescence (LIF) technology can be applied for the detection and localization of bacterial aerosol clouds and bacteria on surfaces from distances exceeding 100 m. It allows fast localization without the need of sample collection. Results are obtained instantly and thus the LIF technology allows fast reaction to biological threats. The technique enables the discrimination of bacteria from other substances in the environment like pollen or chemicals. For identification of bacteria another method like polymerase chain reaction, DNA sequencing or immunological methods may be used in a second step. Fluorescence of approximately fifty different substances was excited using alternating laser pulses with 280 nm and 355 nm with less than 10 mJ, 10 Hz, and less than 10 mJ pulse energy. Measurements were performed outdoors from 22 m distance. Fluorescence spectra were recorded using a spectrometer and an iCCD camera. Measured substances were assigned to four groups: bacteria, plant material, oils and chemicals. Classification algorithms were first trained with part of the dataset and then, in a second step the algorithms were tested with another part of the dataset. Classification of the substances by the algorithms was successfully performed resulting in accuracies of over 90 %. Results are discussed by means of the development of an improved standoff detector.