Aliphatic Disinfection Byproducts Induced Antibiotic Resistance in Escherichia coli through Cell Wall Alteration

Disinfection is a critical step in drinking water treatment, yet studies revealed that it would promote the dissemination of antibiotic resistance, and disinfection byproducts (DBPs) may act as contributors. In this study, we conducted a high-throughput assessment of antibiotic resistance development in the model strain Escherichia coli K12 after 50-day exposure to 15 aliphatic DBPs commonly found in drinking water against 8 different classes of antibiotics. The results showed that most treated bacteria developed resistance to cell wall-targeting antibiotics such as ampicillin and fosfomycin, with resistance levels increasing by 1.16- to 6.39-fold, higher than for other classes of antibiotics. Multidrug resistance was observed in the tribromoacetonitrile (TBAN), bromonitromethane (BNM), and dibromonitromethane (DBNM) groups. DBPs exposure induced the accumulation of reactive oxygen species (ROS) and damaged the bacterial cell membrane. Genomic and transcriptomic analyses revealed mutations and differential expression in genes related to cell wall synthesis and structure, indicating that exposure to DBPs will influence the bacterial cell wall. Nontargeted ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) analysis further confirmed the cell wall structure alteration by the increased proportion of noncanonical d-amino acids in peptidoglycan, the major component of the cell wall, potentially explaining the observed resistance to cell wall-targeting antibiotics. Collectively, this study highlights the risk of aliphatic DBPs-induced antibiotic resistance, likely driven by alterations in the bacterial cell wall.