Production Of Quorum Sensing Signal Moleculars And Effect On Biofilm Formation In Enterobacter Sakazakii

Enterobacter sakazakiiis an opportunistic pathogen associated with meningitis or enteritis in neonates and immunocompromised patients. The organism has been detected in various types of food and in milkprocessing equipment, but only powdered infant formula as a main contamination source, which has been linked to outbreaks ofEnterobacter sakazakii infections. Survival and persistencein such environments may be due to its ability to adhere and form biofilms.Quorum sensing (QS) is a cell to cell communication process that depends on the bacterial population density. Itinvolves small diffusible signaling molecules which activate the expression of target genes that control density-dependent behaviorssuch as, biofilm formation,swarming motility,pigment, exopolysaccharide synthesis, and antibiotic production.Nowadays the strategy to combat bacterial infections withantibiotics is seriously threatened by the spreadof drug-resistant strains, which cause persistent infections,often related to the formation of highly-resistant biofilms.The production of biofilm was strictly interrelated with theexpression of the QS mechanism, but theirmode of action in Enterobacter sakazakii is not clearly understood.This studys aims at detecting N-acyl-homoserine lactones produced by Enterobacter sakazakii and the correlation of N-acyl-homoserine lactones degradationand the formation of biofilm in Enterobacter sakazakii. Moreover, This article also reportsthe anti-quorum sensing activity of herbal essential oil fromFerula that are capable of interfering with thebacterial communication system, but further research will be necessary to identify the activity of Ferula essential oil in E. sakazakii. The main results were as follows:(1) Rapid detection of N-acyl-homoserine lactones was done by bioassays using A. tumefaciensNTL4(pZLR4) and C. violaceum CVO26, The methods including reporter plate bioassays, TLC-Biosensor analysis and β-galactosidase activity assay. These assays is sensitive, simple, reasonably fast with biosensors.(2)Acyl-homoserine lactones (acyl-HSLs) produced by Enterobacter sakazakiiATCC 51329 by the analysis of TLC-Biosensor assay and detected two molecules:(S)-N-3-oxo-hexanoyl-HSL, and (S)-N-oxo-octanoyl-HSL.(3)A chemical study of Acyl-homoserine lactones (acyl-HSLs) produced by Enterobacter sakazakiiATCC 51329 resulted in the identification of five molecules: C12-HSL, C14-HSL,3-oxo-C4-HSL,3-OH-C8-HSL and UHQ, using HPLC-MS.(4)The acyl-HSLs produced by E. sakazakiiwas depleted by A. tumefaciens NT1 (pZRL4) (pME6863), suggesting acyl-HSL degradation by A. tumefaciens NT1 (pZRL4) (pME6863)hydrolases. the expression of hydrolases by A. tumefaciens NT1 (pZRL4) (pME6863) also reduced the biofilm production byE. sakazakii. These results indicated that there was relationship between production of biofilm and the concentration of acyl-HSLs.(5)Broth microdilution method was developed to evaluate the antibacterial activity ofFerula essential oil (FEO), andQuorum sensing (QS) inhibitoryactivityof FEOwasevaluatedusingChromobacteriumviolaceumasbacterialmodel.FEO exertedsignificantpigmentinhibitionwithout affecting C. violacemmgrowth.These results show that FEO are capable of interfering with quorum sensing system in Chromobacteriumviolaceum as a novel QS inhibitor.