Determination of Live and Dead Bacteria with a Novel Handheld Instrument and Raman Spectroscopy

Abstract

Fast identification of live and dead (inactivated) bacteria in situ, whether it is a hospital or field, is a challenging problem. Typically, counting live and dead bacteria requires more than 24 hours (for plating, CFU growth and counting etc.), during which time bacterial infections can grow many fold (bacteria can double in as short as 10 minutes times). In this research, a handheld instrument was designed and constructed which can be carried to the field and can be used for in-situ detection of live and dead bacteria ratio within a few minutes. This handheld instrument is based on the detection of fluorescence from tryptophan and tyrosine present in bacteria. As bacteria are inactivated by UV radiation, fluorescence from tryptophan and tyrosine decreases. By measuring this fluorescence using the developed handheld device, it was possible to determine live and dead bacteria in a sample. Alongside, Raman spectroscopy was explored to determine live and dead bacteria after ultraviolet light inactivation. It was found that there exist a quantitative relationship between changes in Raman spectra of bacteria and number of inactivated cells in a sample.