Bacterial resistance to antibiotics has become a major public health problem in recent years. The occurrence of antibiotics in the environment, especially in wastewater treatment plants, has contributed to the development of antibiotic-resistant bacteria (ARB) and the spread of antibiotic resistance genes (ARGs). Despite the potential of some conventional processes used in wastewater treatment plants, the removal of ARB and ARGs remains a challenge that requires further research and development of new technologies to avoid the release of emerging contaminants into aquatic environments. Non-thermal atmospheric pressure plasmas (NTAPPs) have gained a significant amount of interest for wastewater treatment due to their oxidizing potential. They have shown their effectiveness in the inactivation of a wide range of bacteria in several fields. In this review, we discuss the application of NTAPPs for the degradation of antibiotic resistance genes in wastewater treatment.

Atmospheric pressure plasma processes have been increasingly studied for the microbiological decontamination of liquids. Plasma discharges produce a series of reactive oxygen and nitrogen species (RONS) that diffuse through cell membranes, triggering complex biochemical processes leading to physical and chemical changes in bacteria. The efficiency of plasma liquid decontamination is influenced by the Gram type of bacteria, the bacterial strain, the cell density, and the physiological state of bacteria. The objective of this study was to examine how bacterial growth phases affect the efficiency of plasma liquid decontamination. An atmospheric plasma multijet was used to treat Escherichia coli K12, in the midexponential and stationary phases of growth. The plasma discharge was characterized by optical emission spectroscopy, and the reactive oxygen and nitrogen species (RONS) formed in the treated liquid were quantified by spectrophotometry. The viability assays showed that the growth phase of bacteria influences the effectiveness of the treatment. Cells in the midexponential phase were more susceptible to plasma treatment than stationary-phase cells. After 30 min of plasma treatment, the plasma produced a complete inactivation 7 log reduction in bacteria in the midexponential phase while only a 3 log reduction was observed in stationary phase. Metabolic activity and membrane integrity measurements confirmed the increased sensitivity of exponential phase bacteria compared to stationary cells. In order to study the mechanisms involved in the bactericidal process and cellular defense against plasma-induced oxidative stress, we focused on intracellular ROS levels and genomic DNA damage. The results show a significant difference in intracellular ROS levels between the two phases of growth. However, DNA degradation extent did not reveal any significant differences. These results suggest that a combination of physiological and metabolic responses determine bacterial survival for both growth phases after exposure to plasma treatment.