Effect of electron beam irradiation and the presence of antibiotics on the population ratio of resistant/sensitive bacterial cultures in model wastewater matrix
Control strategies against the spread of antibiotic resistance should be considered in wastewater treatment plants. It is important to understand how resistant bacteria behave in the presence of trace amounts of antibiotics, in order to implement appropriate measures. In our work, we examined the population dynamics of resistant/sensitive Staphylococcus aureus co-cultures. On the one hand, we gained insight into the effect of trace amounts of antibiotics (piperacillin and erythromycin) on bacteria in different wastewater matrices, and on the other hand, we studied the applicability of electron radiation to eliminate the antibacterial effect. Based on our results, trace amounts of antibiotics act on the resistant strain. Presumably, it triggers biological processes in resistant bacteria that do not provide a competitive benefit but disadvantage over the sensitive subtype, and the trace level of the antibiotic present does not appear to affect the sensitive strains. The effect of these conditions on population dynamics is reduced with the use of treatment with accelerated electrons, presumably due to the fact that the decomposition products of the components of the effluent matrix (such as humic acid) also contribute to the chemical transformations. Furthermore, it has become apparent that the presence of trace amounts of antibiotics on the one hand initiates biochemical processes in the resistant subtype and on the other hand sensitizes bacteria to the attack of free radicals generated during electron beam treatment. It is clear that better understanding is needed on the effects of trace level of antibiotics in environmental waters on the cellular response and population behavior of resistant bacterial cultures
