Tracking virulence factor genes and their combination with resistance genes for microbial risk assessment in drinking water treatment plants

Virulence factor genes (VFGs) and their intragenomic combinations with antibiotic resistance genes (ARGs) have been recognized as important targets for microbiological health risk assessment. Yet, their dynamics during drinking water treatment plants (DWTPs) remain unknown. Herein, we conducted an advanced VFG-centric metagenomic strategy to track the fate of VFGs and the intragenomic combination of VFG and ARG during two full-scale DWTPs. We detected 197 VFGs belonging to 12 categories in the two DWTPs by metagenomic sequencing. Both DWTPs elevated the relative abundance of total VFGs, revealing the potential microbial health risks during drinking water treatment. The post-ozonation unit could promote the relative abundance of 8 dominant VFG categories (0.09–3.02-log₁₀). We identified 59 intragenomic VFG-ARG combinations (including 17 combinations of VFG and multiple ARGs) via metagenomic assembly. The DWTP adopting ozone-biological activated carbon treatment processes was revealed to induce the integration of VFG and ARG (even multiple ARGs), which might promote the microbial health risk for effluent. Mycobacterium, Acidovorax, Pseudomonas, and Novosphingobium genera were identified as the primary hosts for VFGs and crucial factors affecting the VFG dynamics during two DWTPs. This research provides new insights into the assessment and control of microbial health risks in drinking water treatment.