Why This Matters:
- VBNC pathogens - bacteria that remain alive but undetectable by standard culture based methods - represent a hidden risk in drinking water systems because they retain metabolic activity and can resuscitate under favorable conditions.
- Traditional culture-based monitoring substantially underestimates VBNC pathogen levels, potentially providing a false assurance of safety.
- This study highlights the need for improved detection and risk assessment strategies for drinking water safety.
Key Findings:
Ni et al. investigated VBNC E. coli and P. aeruginosa across source water, tap water, and potable water collected from 54 source points over a period of six months in a megacity of eastern China, using propidium monoazide quantitative PCR (PMA-qPCR) combined with traditional culture methods.1 They additionally developed multiple linear regression (MLR)- and artificial neural network (ANN)- based predictive models based on routine water quality parameters and performed quantitative microbial risk assessment (QMRA).
- VBNC pathogens remain after standard treatment: Although water treatment reduced VBNC pathogen levels by 1–3 log units, VBNC E. coli and P. aeruginosa were still detected in tap and potable water at concentrations ranging from 100 - 102 CFU/100 mL, with detection rates between 83.3% and 100%.
- Potable water showed higher VBNC levels than tap water possibly due to seeding from faucets or water dispensers.
- ANN-based modeling predicts VBNC levels more accurately compared to MLR based using conventional water quality indicators, with prediction accuracies of 88.9% for E. coli and 77.8% for P. aeruginosa.
- QMRA indicated that annual infection risks and disease burdens from VBNC pathogens in both tap and potable water exceeded acceptable safety benchmarks.
Bigger Picture:
This study underscores that VBNC pathogens - dormant but viable microbes invisible to culture-based tests - can persist through conventional drinking-water treatment and pose quantifiable health risks. Water utilities and public health agencies must therefore augment monitoring strategies to include culture-independent techniques (such as PMA-qPCR) and predictive modelling to assess microbial safety more accurately. Moreover, predictive models such as ANN can help water managers anticipate VBNC pathogen trends based on routine water quality parameters. For risk assessors and regulators, these findings highlight a gap in current drinking water quality frameworks and suggest that VBNC pathogen monitoring may be essential for protecting public health.
(Image Credit: iStock/Sonmez)
References:
- 1. Ni et al. (2025). Occurrence, Predictive Models and Potential Health Risk Assessment of Viable But Non-Culturable (VBNC) Pathogens in Drinking Water. Environmental Pollution.
