Higher Susceptibility of E. coli O157:H7 and Carbapenem-Resistant E. coli Biofilm to the Amalgam Lamp Compared to the Conventional LP Lamp and Mechanism Identification Using Transcriptome Analysis

Abstract This study aimed to assess the susceptibility of Escherichia coli O157 and carbapenem-resistant E. coli biofilm mixtures on stainless steel surfaces to conventional low-pressure (LP) UV and amalgam lamps. Biofilms of E. coli O157 and carbapenem-resistant E. coli were exposed to the LP and amalgam lamps at the same treatment dose for the comparison, and the amalgam lamp achieved significantly higher biofilm reduction levels. Transcriptome analysis was conducted on E. coli O157 ATCC 35150 biofilms with and without amalgam treatment, and the results revealed distinct genetic responses to amalgam treatment. Genes related to stress response, DNA repair, ribosomes, protein folding, phage shock response, carbon source utilization, and biofilm suppression were upregulated after amalgam treatment. Among the differentially expressed genes, those involved in protein synthesis (translation) were notably overexpressed following amalgam treatment. Consequently, gallic and malic acids, known to impact protein synthesis, were combined with amalgam treatment, significantly enhancing biofilm reduction compared with amalgam treatment alone. This study suggests that amalgam treatment may serve as an effective non-thermal alternative to conventional LP UV lamps for biofilm inhibition, with a combination of gallic acid offering a synergistic effect.