Background: Quercus gall extracts' ability to kill pathogens in vitro and even removal of chronic drug-resistant infections has been reported by several studies. The current investigation is focused on the action of extracts of Quercus infectoria gall in their sub-inhibitory concentrations on the corresponding bacterial behaviours instead of killing them. Methods: The effect of gall extracts on the quorum sensing (QS) associated virulence of multiple drug resistant Pseudomonas aeruginosa recovered from burns wounds was studied. The influence of different extracts on the production of bacterial virulence and biofilm, and expression of the genes encoding quorum sensing and exotoxin A were investigated. Quorum sensing is a crucial regulator of virulence and biofilm development in Pseudomonas aeruginosa and other medical related microbes. Results: Experiments to characterise and quantify Q. infectoria gall extracts impact on the quorum sensing networks of P.aeruginosa revealed that the expression of las, rhl, and exotoxin A (ETA) genes levels including the associated virulence were reduced by the extracts at their subinhibitory concentrations. Conclusions: The obtained results indicated that extracts of Q. infectoria galls fight infections either by their inhibitory constituents, which vigorously eradicate cells or by disruption of the pathogens quorum sensing system through weakening the virulence and bacterial coordination.

Pomegranate Peel extractions used as quorum sensing inhibitor (QSI) against Staphylococcus aureus (which isolated from soft white cheese in local market), different solvents used to obtain different active ingredient groups, minimum inhibitory concentration of each group were determined then sub-inhibitory concentration was used as (QSI). We get that all groups have ability to inhibit quorum sensing in Staphylococcus aureus in different ratio. By using Real-time PCR found that the different Pomegranate Peel extract groups can inhibit the expression of some quorum sensing and virulence factor genes ( Sea, Seb, AgrA, RNAIII, and Hla). Also Pomegranate Peel extracts groups have a role in biofilm reduction in Staphylococcus aureus significantly, furthermore the extract groups significantly affect the growth curve of this bacteria. Our results idicated that the pomegranate peel extracts fight infections by supressing virulence factors, may be due to blocking autoinducer receptors.