Review Article
Thavrin Manickum
Abstract
We currently use the gold standard HPC test method for bacterial enumeration of our raw, drinking and waste water; analysis times are relatively long: 1-3 d, as per the international standard reference method. Our tests are accredited to ISO/IEC 17025 requirements. The literature has indicated international use of the current HPC method for monitoring routine microbiological quality of drinking water; current tests for pathogen monitoring have poor sensitivity, accuracy and long analysis times, in general. The aim of this current review is to: Consider shortfalls of the HPC method, Discuss alternative methods for bacterial enumeration, Discuss features and applications of the automated -sample preparation flow cytometer, the BactoSense model, Highlight advantages of flow cytometry, which makes this technique the choice for the bacteriological enumeration in water, and Propose options for standardization of flow cytometry TCC test methods. Findings indicate that HPC is very inaccurate (~ -99% bias), and time-consuming (1-3 d), compared to flow cytometry (~ 99% accurate; ± 15-20 min analysis time). The evidence confirms a strong preference for the use of flow cytometry for Total Cell Counts/mL; the BactoSense is one viable instrument due to its automated sample preparation, speed of analysis, accuracy and precision. There was a significant gap regarding the standardization of current flow cytometry test methods. Options for standardization are ISO/IEC 17025 accreditation, the US EPA, ASTM, AOAC, and Standard Methods. Some key method validation parameters are: accuracy, bias, precision, specificity, LOD, LOQ, linearity, and the Uncertainty of measurement. The review has highlighted the potential of flow cytometry for the screening of Corona virus SARS-CoV-2 for COVID-19. The BactoSense FCM appears to be a viable option for bacterial enumeration, as a TCC/mL measure, for drinking water, due to its sample preparation automation, speed of analysis, accuracy and precision. The current, and new, FCM test methods should be validated, standardized, or accredited for adoption for bacterial enumeration of water. Flow cytometry is the preferred test method for bacterial enumeration of water - it should replace the HPC method.