Aim: To study the bactericidal activity of crude ethanolic extract and fractionations obtained from Sargassum aquifolium (Turner) C. Agardh (brown algae) towards Gram-positive bacteria and Gram-negative biofilm-forming human pathogenic bacteria.

Background: The increasing emergence of antibiotic-resistant bacteria in the hospital and community settings has led to the discovery of alternative strategies. Marine organisms are considered as one of the potential sources of diverse bioactive molecules against several biological activities. Hence, the algae, especially the marine brown algae were selected to evaluate its antibacterial activities towards biofilm-forming human pathogenic bacteria.

Objective: To restrain the drug-resistant ability of pathogenic bacteria, we checked the extract of Sargassum aquifolium (Turner) C. Agardh (Phyophyceae) for the concerned bioactive compounds.

Methods: Antibacterial activity towards both Gram-positive and Gram-negative bacteria was evaluated using disk diffusion and broth microdilution assays. Furthermore, the active compound present in the extracts was also identified using Gas-Chromatography-Mass Spectroscopy (GC-MS).

Results: A total of 21 bioactive compounds were identified using GC-MS analysis with different chemical natures. The crude ethanolic extraction was fractionated sequentially according to the eluotropic series from less to extreme polar. The highest zone of inhibition was recorded for ethanolic extract on Listeria monocytogenes with a value of 38.00±0.17 mm and the lowest was 10.67±0.06 mm for ethyl acetate fraction on Pseudomonas aeruginosa. Ethyl acetate fractionate showed a higher effectivity than other fractionations. An MIC value of 256 μg/mL was recorded against Staphylococcus aureus and L. monocytogenes and 512 μg/mL against Escherichia coli and P. aeruginosa. Its ethanolic extract also showed synergism with oxytetracycline on S. aureus, L. monocytogenes, and E. coli. Furthermore, the same extracts also showed synergism with tetracycline on E. coli and with erythromycin on P. aeruginosa.

Conclusion: The present study reports the antibacterial activity of the S. aquifolium (Turner) C. Agardh extracts against human pathogenic bacteria. Furthermore, it also predicts the synergistic activity of selected antibiotic combinations against both selected Gram-positive and Gram-negative pathogenic bacteria.

目的：研究从马尾藻 (Turner) C. Agardh（褐藻）中获得的粗乙醇提取物和分级分离物对革兰氏阳性菌和革兰氏阴性生物膜形成人类致病菌的杀菌活性。

背景：医院和社区环境中抗生素耐药细菌的不断出现导致了替代策略的发现。海洋生物被认为是针对多种生物活性的多种生物活性分子的潜在来源之一。因此，选择藻类，特别是海洋褐藻来评估其对形成生物膜的人类致病菌的抗菌活性。

目的：为了抑制病原菌的耐药能力，对藻藻纲马尾藻提取物中的相关生物活性成分进行检测。

方法：使用纸片扩散和肉汤微量稀释测定评估对革兰氏阳性菌和革兰氏阴性菌的抗菌活性。此外，还使用气相色谱-质谱法 (GC-MS) 鉴定了提取物中存在的活性化合物。

结果：通过 GC-MS 分析，共鉴定出 21 种具有不同化学性质的生物活性化合物。根据洗脱系列从弱极性到极端极性对粗乙醇提取物进行顺序分级。乙醇提取物对单核细胞增生李斯特氏菌的抑菌圈最高，为 38.00±0.17 mm，而乙酸乙酯馏分对铜绿假单胞菌的抑菌圈最低，为 10.67±0.06 mm。乙酸乙酯分馏比其他分馏显示出更高的效率。针对金黄色葡萄球菌和单核细胞增生李斯特菌的 MIC 值为 256 μg/mL，针对大肠杆菌和铜绿假单胞菌的 MIC 值为 512 μg/mL。其乙醇提取物还与土霉素对金黄色葡萄球菌、单核细胞增生李斯特菌和大肠杆菌具有协同作用。此外，相同的提取物还显示出与四环素对大肠杆菌具有协同作用，与红霉素对铜绿假单胞菌具有协同作用。

结论：本研究报告了 S. aquifolium (Turner) C. Agardh 提取物对人类致病菌的抗菌活性。此外，它还预测了选定的抗生素组合针对选定的革兰氏阳性和革兰氏阴性病原菌的协同活性。