Rapid and Accurate Quantification of Bacterial Cells in Fresh Water Using a Simplified Microfluidic Device

The prevention of waterborne outbreaks associated with contaminated water is one of the most important topics in closed habitation. We investigated the ability of a newly designed microfluidic device to determine bacterial numbers in freshwater. A microfluidic device was designed and fabricated by polydimethylsiloxane (size: 50 mm × 24 mm). A fluorescent microscope-based system was used for enumeration of cells flowing rapidly through the microchannel. The numbers of E. coli cells suspended in filtrated sterilized water at a density in the order of 10⁴ - 10⁶ /ml determined by this on-chip flow cytometer were similar with the microscopic counts. The time required for enumeration by on-chip flow cytometer was approximately 10 min per sample. This simple enumeration method will contribute to the technical progress in microbiological quality control of fresh water used in CELSS.