AFI Corp. PixeeMo™ for Enumeration of Aerobic Bacteria in Drinking Water: AOAC Performance Tested MethodSM 012002.

Background: PixeeMo™ is a compact instrument that enables bacterial cell counting using microfluidic chips instead of counting of colonies on culture media. Chips containing electrodes, based on fluid, electric filtering and sorting technology (FES), allow the selection of bacterial cells from other components in the sample. In the United States (US), surface water or ground water affected by surface water must be treated to reduce the total microbial load to less than 500 CFU/mL. In Japan, drinking water regulations limit the total bacterial load to 100 CFU/mL.

Objective: To validate the PixeeMoTM aerobic bacteria method based on the Japanese regulation in the range of 30-300 CFU/mL in drinking water.

Method: PixeeMoTM aerobic bacteria method was compared to the Standard Method for the Examination of Water and Wastewater (SMEWW) 9215B (2017) using naturally contaminated drinking water.

Results: The maximum repeatability standard deviation of the PixeeMoTM method was 14.8%. The difference of mean log10 values between the PixeeMoTM and SMEWW 9215B methods ranged from -0.015 to 0.258. Similar results were obtained in the independent laboratory study.

Conclusions: The PixeeMoTM method is equivalent to that of the SMEWW 9215B methods. The product consistency and stability study demonstrated no significant difference within the expiration date. The robustness study confirmed that there was no effect within the expected range. The instrument variation study also demonstrated no significant difference among the data of three PixeeMoTM instruments.

Highlights: Total counts of bacteria in drinking water can be determined accurately within 1 h with PixeeMoTM.