A rapid and low-cost estimation of bacteria counts in solution using fluorescence spectroscopy

Area of Science:

• Microbiology
• Analytical Chemistry
• Spectroscopy

Background:

• Accurate bacterial enumeration is crucial for various applications.
• Traditional methods can be time-consuming and costly.
• Rapid, cost-effective bacterial detection methods are needed.

Purpose of the Study:

• To investigate the use of acridine orange (AO) fluorescence spectra for rapid bacterial enumeration.
• To develop a classification model for bacterial concentration based on spectral data.
• To assess the feasibility of a rapid, low-cost microbiological testing method.

Main Methods:

• Bacterial samples (Escherichia coli) were stained with varying concentrations of AO.
• Fluorescence spectra were recorded using a fiber-based spectroscopic system.
• Independent component analysis (ICA) was applied to spectral datasets for classification.

Main Results:

• The relationship between AO fluorescence intensity and bacterial concentration was non-linear.
• Spectral signals were reproducible and unique, enabling sample classification.
• Bacterial concentration order of magnitude (above 10^5 CFU/ml) could be rapidly determined using specific sample preparation methods.

Conclusions:

• Fluorescence spectroscopy of bound AO offers a rapid and reproducible method for bacterial enumeration.
• The developed method provides order-of-magnitude bacterial concentration information within 25 minutes.
• This technique presents a cost-effective alternative for microbiological tests requiring gross concentration data.