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首页> 外文期刊>Applied Microbiology >Catalase Expression Is Modulated by Vancomycin and Ciprofloxacin and Influences the Formation of Free Radicals in Staphylococcus aureus Cultures
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Catalase Expression Is Modulated by Vancomycin and Ciprofloxacin and Influences the Formation of Free Radicals in Staphylococcus aureus Cultures

机译：万古霉素和环丙沙星调节过氧化氢酶的表达，并影响金黄色葡萄球菌培养物中自由基的形成。

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Detection of free radicals in biological systems is challenging due to their short half-lives. We have applied electron spin resonance (ESR) spectroscopy combined with spin traps using the probes PBN ( N-tert -butyl-α-phenylnitrone) and DMPO (5,5-dimethyl-1-pyrroline N -oxide) to assess free radical formation in the human pathogen Staphylococcus aureus treated with a bactericidal antibiotic, vancomycin or ciprofloxacin. While we were unable to detect ESR signals in bacterial cells, hydroxyl radicals were observed in the supernatant of bacterial cell cultures. Surprisingly, the strongest signal was detected in broth medium without bacterial cells present and it was mitigated by iron chelation or by addition of catalase, which catalyzes the decomposition of hydrogen peroxide to water and oxygen. This suggests that the signal originates from hydroxyl radicals formed by the Fenton reaction, in which iron is oxidized by hydrogen peroxide. Previously, hydroxyl radicals have been proposed to be generated within bacterial cells in response to bactericidal antibiotics. We found that when S. aureus was exposed to vancomycin or ciprofloxacin, hydroxyl radical formation in the broth was indeed increased compared to the level seen with untreated bacterial cells. However, S. aureus cells express catalase, and the antibiotic-mediated increase in hydroxyl radical formation was correlated with reduced katA expression and catalase activity in the presence of either antibiotic. Therefore, our results show that in S. aureus , bactericidal antibiotics modulate catalase expression, which in turn influences the formation of free radicals in the surrounding broth medium. If similar regulation is found in other bacterial species, it might explain why bactericidal antibiotics are perceived as inducing formation of free radicals.
机译：由于半衰期短，因此在生物系统中检测自由基具有挑战性。我们使用电子自旋共振（ESR）光谱结合自旋阱，使用探针PBN（N-叔丁基-α-苯基硝基）和DMPO（5,5-二甲基-1-吡咯啉N-氧化物）评估自由基的形成在人类病原体金黄色葡萄球菌中用杀菌抗生素，万古霉素或环丙沙星治疗。尽管我们无法在细菌细胞中检测到ESR信号，但在细菌细胞培养物的上清液中却观察到了羟基自由基。出乎意料的是，在没有细菌细胞的肉汤培养基中检测到最强的信号，并且铁螯合或添加过氧化氢酶（可催化过氧化氢分解为水和氧气）减弱了该信号。这表明该信号源自芬顿反应形成的羟基自由基，其中铁被过氧化氢氧化。以前，已提出响应细菌性抗生素在细菌细胞内产生羟基自由基。我们发现，当金黄色葡萄球菌暴露于万古霉素或环丙沙星时，与未经处理的细菌细胞相比，肉汤中的羟基自由基形成确实增加了。然而，金黄色葡萄球菌细胞表达过氧化氢酶，并且在两种抗生素存在下，抗生素介导的羟基自由基形成的增加与减少的katA表达和过氧化氢酶活性相关。因此，我们的结果表明，在金黄色葡萄球菌中，杀菌抗生素可调节过氧化氢酶的表达，进而影响周围肉汤培养基中自由基的形成。如果在其他细菌物种中发现了类似的规定，则可能解释了为什么杀菌抗生素被认为诱导自由基的形成。

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