Data supporting the research of Regrowth of Specific Bacterial Pathogens and AMR in Ozonated Wastewater Effluent

Ozonation is increasingly applied in advanced wastewater treatment to reduce micropollutants but has been linked with survival and regrowth of pathogenic bacteria and antibiotic resistance genes (ARGs). The extent of regrowth following low-dose ozonation, representative of full-scale operation, remainspoorly understood. Here, we investigated microbial survival, post-treatment growth, and ARG redistribution in ozonated wastewater effluent during storage. Survival and growth of Pseudomonas aeruginosa were assessed using culturing and propidium monoazide (PMA)–qPCR, while broader pathogen and resistome dynamics were examined by PMA-metagenomics. Intracellular (iDNA) and extracellular DNA (exDNA) fractions were analyzed separately. Low-dose ozonation did not affect P. aeruginosa and increased during storage and exceeded pre-treatment abundances after three days. Consistent temporal patterns across methods supported the applicability of PMA-metagenomics for tracking viable pathogens and ARGs. Similar growth trends were observed for opportunistic pathogens, including Enterobacter hormaechei and Klebsiella pneumoniae. Immediately after ozonation, reductions in iDNA coincided with increased detection in exDNA, indicating cellular damage and DNA release; this pattern partially reversed during storage. Surviving populations were relatively enriched in macrolide resistance genes, while regrowing taxa were associated with increased relative abundances of β-lactam and multidrug efflux pump ARGs. These findings demonstrate that low-dose ozonation reshapes pathogen and ARG composition and may facilitate post-treatment growth, underscoring the need for absolute quantification to support microbial risk assessment in wastewater reuse.