(521c) Determination of the Number of Bacteria Based on Autofluorescence on a Microfluidic Chip

Bacterial counts are often determined for hygiene monitoring of products. In this study, we demonstrate the quantification of the number of bacterial cells based on the autofluorescence from the cell lysate on a microfluidic chip. We tested three model pathogenic bacteria (Listeria monocytogenes F4244, Salmonella Enteritidis PT1 and Escherichia coli O157:H7 EDL 933). In the experiment, a plug of ~150 pL containing lysate from 240 to 4100 cells was injected into a microfluidic channel with downstream laser-induced fluorescence detection under electrophoresis conditions. We found that the autofluorescence intensity increased with the number of cells almost linearly for all three bacteria. The autofluorescence remained a single peak when the cell lysate contained a mixture of different bacterial species. Our method offers a simple solution to the quantification of bacterial cells without any labeling, especially on a microchip platform. We believe that the method can be extended to other bacterial species.