biostudies-literatureOu FMinistry of Business, Innovation and Employment4807https://www.ebi.ac.uk/biostudies/studies/S-EPMC6423134biostudies-literatureUnknown9(1)A rapid, cost-effective and easy method that allows on-site determination of the concentration of live and dead bacterial cells using a fibre-based spectroscopic device (the optrode system) is proposed and demonstrated. Identification of live and dead bacteria was achieved by using the commercially available dyes SYTO 9 and propidium iodide, and fluorescence spectra were measured by the optrode. Three spectral processing methods were evaluated for their effectiveness in predicting the original bacterial concentration in the samples: principal components regression (PCR), partial least squares regression (PLSR) and support vector regression (SVR). Without any sample pre-concentration, PCR achieved the most reliable results. It was able to quantify live bacteria from 10⁸ down to 1Scientific reportsNear real-time enumeration of live and dead bacteria using a fibre-based spectroscopic device.PMC6423134UOAX1411McGoverin CVanholsbeeck FOu FSwift SfalseNear real-time enumeration of live and dead bacteria using a fibre-based spectroscopic device.A rapid, cost-effective and easy method that allows on-site determination of the concentration of live and dead bacterial cells using a fibre-based spectroscopic device (the optrode system) is proposed and demonstrated. Identification of live and dead bacteria was achieved by using the commercially available dyes SYTO 9 and propidium iodide, and fluorescence spectra were measured by the optrode. Three spectral processing methods were evaluated for their effectiveness in predicting the original bacterial concentration in the samples: principal components regression (PCR), partial least squares regression (PLSR) and support vector regression (SVR). Without any sample pre-concentration, PCR achieved the most reliable results. It was able to quantify live bacteria from 10⁸ down to 12019-01-01T00:00:00Z2019 Mar2025-04-04T11:08:00.051Z2019-08-03T07:04:27ZS-EPMC64231343088618310.1038/s41598-019-41221-1