Lorestan University of Medical Sciences Herbal Medicines Journal 2538-2144 5 3 2020 05 01 Anti-bacterial and Anti-Quorum Sensing Properties of Dionysia Revolute Boiss against Secondary Bacterial Infections of COVID-19 Patients; An in-vitro Study 91 99 221257 10.22087/herb%20med%20j.v5i3.825 EN Nahal Hadi Department of Bacteriology & Virology, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran Farhad Moradi Department of Bacteriology & Virology, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran Reyhaneh Rohi Jahromi Department of Bacteriology & Zoonoses Research Center, Jahrom University of Medical Sciences, Jahrom, Iran Maryam Akbari Department of Microbiology, Shahid Sadoughi University of Medical Sciences, Yazd, Iran Journal Article 2025 05 20 Background and Aim: Today, the use of traditional plant compounds to kill or interfere with their quorum sensing (QS) mechanisms is considered as an alternative approach to control secondary bacterial infections during or after a viral infection. In this study, anti-bacterial and anti-quorum sensing effect of Dionysia revolute Boiss against five secondary bacterial infections of COVID-19 patients were evaluated.Materials and Methods: Extraction of the plant compounds was carried out using n-hexane, methanol, and 96% ethanol mixed solvent. Bacterial samples were collected from respiratory tract fluids among COVID-19 patients and recognized with API kits. Antibacterial activity of the herbal extract was assessed by disc diffusion method as proposed by the Clinical Laboratory Standards Institute (CLSL, 2015). Hence, anti-QS activities of this herbal extract at the sub-minimum inhibitory concentration (MIC) were assessed by violacein quantification assay in Chromobacterium violaceum CV026 biosensor strains in vitro.Results: As it has been indicated in the Results section, a plant extract from 50 to 0.39 mg/ml exposed their antibacterial impacts via hindering the bacterial growth in comparison with controls and exhibited anti-QS activities via decreasing the violacein formation in C. violaceum CV026 biosensor strain at sub-MIC concentrations (3.1 to 0.39 mg/ml) in vitro.Conclusion: Our study showed that the antimicrobial activities of Dionysia revolute Boiss could be due to their anti-QS properties. Therefore, this medicinal plant either as a stand-alone treatment or in combination with antibiotics could be used as an efficient choice for curing secondary bacterial infections.  https://hmj.lums.ac.ir/article_221257_88fe2bbb97fbc84309690f3110052f4c.pdf