1-(2-氯-4-吡啶)-3-苯基脲又称氯吡脲或膨大剂，是一种重要的植物生长调节剂，属于吡啶取代脲类细胞分裂素，有促进植物生长，增大果实的作用。本实验室前期在筛选氯吡脲的农药降解菌过程中，发现该化合物具有较广谱的抑菌效果。由于氯吡脲生物毒性较低，如果其具有很强的抑菌活性，则该化合物在治疗微生物感染方面有潜在应用价值。因此，本研究旨在评估氯吡脲作为抑菌剂的潜力，所获结果总结如下。

1.氯吡脲对土壤细菌、真菌以及模式细菌的抑制作用

首先，将两种土壤的悬液稀释涂布于含有不同浓度氯吡脲的平板，结果显示，50 μg/mL、75 μg/mL和100 μg/mL氯吡脲对细菌抑菌率能够达到90%以上。50 μg/mL、75 μg/mL和100 μg/mL氯吡脲对放线菌抑菌率基本达到100%，氯吡脲对真菌无显著抑制效果。氯吡脲对模式菌株Bacillus subtilis 168和Escherichia coli DH5α的最低抑菌浓度(MIC)分别为64 μg/mL和128 μg/mL。其次，以B. subtilis 168为材料初步探究了氯吡脲的抑菌机理。结果显示，氯吡脲并没有杀死细菌而是抑制细菌的生长；此外，氯吡脲的作用靶点不是脂肪酸合成酶编码基因fabI和fabL。说明氯吡脲的抑菌机制与其结构类似物三氯生(一种广谱抗菌剂)不同。

2.氯吡脲对常见“超级细菌”有普遍的抑制作用

为了进一步评估氯吡脲作为抑菌剂的潜力，首先收集了5株常见的“超级细菌”，包括耐碳青霉烯类Klebsiella pneumonia、耐碳青霉烯类E. coli、耐万古霉素Enterococcus、耐甲氧西林Staphylococcus argenteus、耐甲氧西林S. simulans，并通过分离纯化、形态特征、系统进化树分析和耐药基因扩增对这些菌株进行了验证。然后，测定了氯吡脲对这些菌株的MIC，结果显示，氯吡脲对耐碳青霉烯类K. pneumonia和耐碳青霉烯类E. coli的MIC为256 μg/mL，对耐万古霉素Enterococcus、耐甲氧西林S. argenteus和耐甲氧西林S. simulans的MIC为64 μg/mL。

综上所述，本研究发现氯吡脲对土壤细菌和常见“超级细菌”具有广谱的抑菌效果，比较氯吡脲对B. subtilis 168、E. coli DH5α和多株常见“超级细菌”的MIC，结果表明该化合物对革兰氏阳性菌的抑制效果强于革兰氏阴性菌。脂肪酸合成酶并非氯吡脲抑菌作用靶点，其抑菌机理仍需进一步探索。氯吡脲对常见“超级细菌”有显著的抑制效果，但对比常用抗生素，氯吡脲对5株“超级细菌”的MIC较高；鉴于氯吡脲本身毒性低、稳定性好，其应用于医学治疗的潜力还需进一步通过动物试验进行评估。

1-(2-chloro-4-pyridine)-3-phenylurea, also known as forchlorfenuron or bulking agent, is an important plant growth regulator. It belongs to pyridine instead of urea cytokinin, which promotes plant growth and increases the role of fruit. In the early stage of this laboratory, in the process of screening microorganisms that could degrade forchlorfenuron, it was unintentionally found that the compound had a broad-spectrum bacteriostatic effect. Due to its low biological toxicity, if it has strong antibacterial activity, the compound has potential application value in the treatment of microbial infections. Therefore, this study aimed to assess the potential of clopicarbamide as a bacteriostat. The results obtained are summarized below.

1. Inhibitory effect of forchlorfenuron on soil bacteria and model strain

Firstly, suspension dilution of the two soils was applied to plates containing different concentrations of forchlorfenuron. The results showed that the bacteriostatic rate of 50 μg/mL, 75 μg/mL and 100 μg/mL of forchlorfenuron could reach more than 90%. The inhibitory rate of 50 μg/mL, 75 μg/mL and 100 μg/mL on actinomycetes was basically 100%, while the inhibitory rate of clopramide on fungi was not significant. The minimum inhibitory concentration (MIC) of chlorfenuron against model strains Bacillus subtilis 168 and Escherichia coli DH5 was 64 μg/mL and 128 μg/mL, respectively. Secondly, using B. subtilis 168 as the material, the antibacterial mechanism of chlorfenuron was preliminarily explored. The results showed that chlorfenuron did not kill bacteria but inhibited their growth. In addition, fabI and fabL, coding genes of fatty acid synthase, do not target forchlorfenuron. It is suggested that the antibacterial mechanism of forchlorfenuron is different from its structural analogue triclosan (a broad-spectrum antibacterial agent)..

2. Forchlorfenuron has a general inhibitory effect on "super bacteria".

To further assess its potential as an antimicrobial agent, we worked with the Jiangsu Provincial Center for Disease Control and Prevention to identify the inhibitory effect of clopramide on common "superbugs". We first collected 5 strains of common "superbacteria", including Carbapenem-resistant Klebsiella pneumonia, Carbapenem- resistant E.coli, Vancomycin-resistant Enterococcus, Methicillin-resistant Staphylococcus argenteus and Methicillin-resistant S.simulans, and validated these strains through morphological characteristics, phylogenetic tree analysis and drug resistance gene expansion. The MIC for forchlorfenuron against these strains was determined and showed that the MIC for Carbapenem-resistant K. pneumonia, Carbapenem-resistant E. coli were 256 μg/mL, and that for Vancomycin-resistant Enterococcus, Methicillin-resistant S. argenteus and Methicillin-resistant S. simulans were 64 μg/mL.

To sum up, this study found that forchlorfenuron had a broad-spectrum inhibitory effect on soil bacteria and common "superbacteria". By comparing MIC of B. subtilis 168, E. coli DH5 and common "superbacteria", the inhibitory effect of this compound on gram-positive bacteria was stronger than that on gram-negative bacteria. Fatty acid synthase is not the target of bacteriostatic action of chlorfenuron. Chlorfenuron had a significant inhibitory effect on common "superbacteria", but compared with common antibiotics, the MIC of forchlorfenuron on 5 "superbacteria" was higher. In view of its low toxicity and good stability, the potential of forchlorfenuron in medical treatment needs to be further evaluated by animal experiments.

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