Short-lived success: repeated peroxide-peracetic acid-based foam disinfection selects for carbapenem-resistant Enterobacterales in hospital sink-drains

Sink-drains/traps in healthcare facilities are recognized reservoirs of drug-resistant Gram-negative bacilli, yet effective remediation strategies remain uncertain. Using culture-based and metagenomic approaches, we evaluated the impact of a peroxide-peracetic acid (PPAA)-foam disinfectant applied at 3-, 5-, or 7-day intervals over four weeks in a controlled Sinklab and a hospital setting. Across all application frequencies and repeated applications, PPAA-foam was ineffective in reducing carbapenemase-producing Enterobacterales counts from baseline over 28days. Instead, treatment induced pronounced microbiome dysbiosis in sink-drains and traps, characterized by reduced community diversity, enrichment of Enterobacterales, and amplification of resistance determinants, including bla KPC and bla NDM . Hospital sinks exhibited comparable transient effects following PPAA-foam treatment, with rapid post-treatment recovery of both microbial communities and resistome. Together, these findings demonstrate that repeated chemical disinfection of established plumbing systems may alter drain microbiomes and paradoxically reinforce the persistence of high-risk pathogens and antimicrobial resistance, underscoring the need for ecologically informed alternatives to chemical-only interventions.