Table of Contents
International Scholarly Research Notices
Volume 2014, Article ID 430412, 7 pages
Research Article

Optical Fiber-Based Steady State and Fluorescence Lifetime Spectroscopy for Rapid Identification and Classification of Bacterial Pathogens Directly from Colonies on Agar Plates

1Department of Medical Physics, Anna University, Chennai 600025, India
2Department of Medical Physics, Red Sea University, P.O. Box 24, Port Sudan, Sudan
3Centre for Advanced Studies in Botany, University of Madras, Chennai 600025, India

Received 4 April 2014; Accepted 9 July 2014; Published 29 September 2014

Academic Editor: João A. Lopes

Copyright © 2014 Fathi Awad et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Fluorescence spectroscopy was examined as a potential technique for identification and classification of bacterial pathogens. Colonies of Staphylococcus aureus, Pseudomonas aeruginosa, Salmonella typhi, and Klebsiella pneumoniae on agar plates were measured directly using a laboratory spectrofluorimeter coupled with optical fiber. Steady state fluorescence spectra were collected following excitation at 280 nm (tryptophan) and 380 nm (NADH). Results showed that fluorescence lifetime decays of tryptophan at 280 nm excitation from the four organisms were best described with triexponential fit and it reveals the existence of different protein conformation. The emission spectroscopy of the four bacteria at 380 nm excitation (NADH) provided better classification (100% of original grouped cases correctly classified and 98.1% of cross-validated grouped cases correctly classified) than that of 280 nm excitation (tryptophan). Our results demonstrated that optical fiber-based fluorescence identification and classification of bacteria is rapid, easy to perform, and of low cost compared to standard methods.