Radiation Chemistry Department, Institute for Energy Security and Environmental Safety, Centre for Energy Research, H-1121, Konkoly-Thege Miklós út 29-33, Budapest, Hungary.
Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing, 100084, PR China.
Chemosphere. 2022 Jan;286(Pt 1):131467. doi: 10.1016/j.chemosphere.2021.131467. Epub 2021 Jul 9.
The chemical changes caused by electron beam and γ irradiations and the biochemical characteristics of degradation products of a frequently used antibiotic oxacillin were investigated and compared with those of cloxacillin by applying pulse radiolysis, chemical and biochemical oxygen demand, total organic carbon content, oxygen uptake rate, toxicity and antibacterial activity measurements. Oxacillin was found to be non-toxic, but poorly biodegradable by the mixed microbial population of the activated sludge of a wastewater treatment plant. Therefore, it can significantly contribute to the spread of β-lactam antibiotic resistant bacteria. However, the products formed by γ-irradiation were more easily biodegradable as they were utilized as nutrient source by the microbes of the activated sludge and the products did not show antibacterial activity. During irradiation treatment of aerated aqueous solutions mainly hydroxyl radicals induce the elimination of antimicrobial activity by making alterations at the bicyclic β-lactam part of these antibiotics. Since the β-lactam part is the same in oxacillin and cloxacillin, the biochemical characteristics of products of the two antibiotics are similar. The attack of hydrated electron takes place on the carbonyl groups. When the irradiation is made under anoxic conditions these reactions may also contribute considerably to alterations at the β-lactam part and thereby to the loss of antibacterial activity.
研究了电子束和γ辐照引起的化学变化以及常用抗生素苯唑西林的降解产物的生化特性，并通过脉冲辐射、化学需氧量、生化需氧量、总有机碳含量、耗氧速率、毒性和抗菌活性测量，将其与氯唑西林进行了比较。
研究发现，苯唑西林对混合微生物种群（来自废水处理厂的活性污泥）没有毒性，但生物降解性较差。因此，它可以显著促进β-内酰胺类抗生素耐药菌的传播。然而，γ 辐照形成的产物更容易生物降解，因为它们可以被活性污泥中的微生物用作营养源，而且这些产物没有表现出抗菌活性。
在有氧水溶液的辐照处理中，主要是羟基自由基通过改变这些抗生素的双环β-内酰胺部分来消除抗菌活性。由于苯唑西林和氯唑西林的β-内酰胺部分相同，因此两种抗生素产物的生化特性相似。水合电子的攻击发生在羰基上。当在缺氧条件下进行辐照时，这些反应也可能对β-内酰胺部分的改变产生很大影响，从而导致抗菌活性丧失。
