Prolonged electrochemical/antibiotic stresses promoted the cross-resistance of disinfection-residual-bacteria.

How to achieve efficient control of antibiotic resistance in water/wastewater advanced treatment has become a critical global concern. Disinfection-residual-bacteria (DRB) was often reported to be associated with antibiotic resistance, and their cross-resistance of disinfectants (disinfection methods) and antibiotics complicates the potential risk after disinfection. Electrochemical disinfection showed high efficacy in antibiotic resistance control, while prolonged evolution of cross-resistance of DRB under both antibiotic and electrochemical stresses was still unclear. The results indicated that the lower metabolic rates and higher cell membrane strength contributed to bacterial cross-resistance for antibiotic-resistant E. coli compared with antibiotic-sensitive E. coli. Continuous exposure to antibiotic and electrochemical stress promoted the evolution of cross-resistance in antibiotic-sensitive E. coli. In detail, the electrochemical sterilization rate decreased from 0.96 to 0.63 within 5 days, and its antibiotic resistance rapidly evolved and reached the same level as antibiotic-resistant E. coli within 9 days. This confirmed that continuous stress promoted E. coli to develop the non-heritable resistance phenotype in a short period. Further analysis indicated that both antibiotic and electrochemical stresses induced similar mutations in DNA sequences in cell division, cellular stress responses, as well as biofilm formation and transport. This work evaluated the evolution level of bacterial cross-resistance and further revealed the evolution mechanisms during electrochemical disinfection. The results would be useful in comprehensive evaluation of disinfection efficiency by incorporated consideration of potential evolution of DRB's cross-resistance.