QUANTOM Tx™ Microbial Cell Counter for Rapid Enumeration
Comparison with existing bacterial counting methodsdownload pdf
- Counting with the QUANTOM Tx Microbial Cell Counter
- Accurate determination of standard bead counts by the QUANTOM TxThe counting accuracy of the QUANTOM Tx was confirmed by counting standard fluorescent beads of known concentration. Beads were serially diluted, mixed with the QUANTOM Cell Loading Buffer I, and loaded into a QUANTOM M50 Cell Counting Slide. The slide was spun in the QUANTOM Centrifuge at 300 RCF for 10 minutes to ensure even bead distribution and then counted with the following parameters with the QUANTOM Tx: LED = Bead, size = 1-50 μm, detection sensitivity = 0, declustering level = 7, roundness = 30%. All counts were performed in triplicate. As demonstrated in Figure 1, the QUANTOM Tx produced results with a a strong correlation (R2 = 0.9997) to the theoretical concentration of beads.
- Figure 1. Correlation between known standard bead concentrations and QUANTOM Tx results.
- Accuracy and variability compared to a flow cytometer and a hemocytometerTo compare the accuracy of the QUANTOM Tx compared to a flow cytometer and hemocytometer, serial dilutions of Escherichia coli were counted in triplicate. For the flow cytometer, cells were stained with Thiazol Orange and counted with the FACSCalibur flow cytometer (BD Biosciences). Standard beads were added to help determine cell concentration. For the hemocytometer, cells were loaded into a Petroff-Hausser Counting Chamber (20 μm, Hausser Scientific) and imaged with the CELENA S Digital Imaging System (Logos Biosystems) using a TC PlanAchro 20x Ph objective. Five squares of the Neubauer counting grids were counted. For the QUANTOM Tx, cells were stained with QUANTOM Total Staining Dye and counted with the following parameters: LED = 5, size = 0.3-50 μm, detection sensitivity = 0, declustering level = 0, roundness =0%. There was no significant difference in the total concentrations, but the hemocytometer showed a higher variability from count to count as cell concentration increased whereas the QUANTOM Tx and flow cytometer had more consistent results (Figure 2).
- Figure 2. Comparison of counting results from the QUANTOM Tx, a flow cytometer, and a hemocytometer.
- Adjustable protocols detect bacterial cells of various morphologies and arrangementsTo demonstrate the versatility of the QUANTOM Tx, various bacteria species were stained with QUANTOM Total Staining Dye and counted with the QUANTOM Tx. The QUANTOM Tx automatically captures, analyzes, and labels up to 20 high-resolution images per count, making it easy to verify the accuracy of each count visually. Lactobacillus casei were counted with the following parameters : LED = 5, size = 1-50 μm, detection sensitivity = 0, declustering level = 7, roundness =0. Bacillus megaterium were counted with the following parameters: LED = 5, size = 1-50 μm, detection sensitivity = 3, declustering level = 10, roundness =0. A more complete list of bacteria and the parameters used to count them can be found at: goo.gl/ixr8kr. As shown in Figure 3, the QUANTOM Tx was able to distinguish individual cells in the tight bacilli chains.
- Figure 3. Individual bacilli in chains detected using the QUANTOM Tx declustering feature. Lactobacillus casei (L) and Bacillus megaterium (R) were counted with the QUANTOM Tx with the declustering levels set to 7 and 10, respectively.
- A partial list of bacteria tested on the QUANTOM Tx