Inhibitory Effects Of Thymol,Carvacrol And Cinnamaldehyde On Salmonella And Its Biofilm In Retail Chicken

Salmonella is considered one of the major foodborne pathogens associated with food safety.The clinical symptoms of Salmonella infection include fever,gastroenteritis and food poisoning.The biofilm adhering to food surfaces and processing equipment is even more difficult to eliminate.Thymol,carvacrol and cinnamaldehyde,as potential natural antibacterial agents,have good inhibitory effects on Salmonella.However,little information on their antibacterial preservation effects on chicken is available,and there is a lack of research on the inhibition of biofilm formation of Salmonella.Therefore,the prevalence of Salmonella isolated from retail meats in Hefei was firstly investigated,and Salmonella was further characterized by antimicrobial resistance,antimicrobial resistance genes,and virulence genes.The effect of thymol,carvacrol and cinnamaldehyde as natural antimicrobial agents on the inhibition of Salmonella isolates and storage characteristics during storage of chicken was studied.Then the inhibitory effects of these three components on Salmonella biofilm development(formation and dissociation)were investigated by crystalline violet staining,metabolic capacity measurement,scanning electron microscopy(SEM)and confocal laser scanning microscope(CLSM)observation.The research results are as follows:(1)Out of the 120 samples of retail pork,chicken and duck collected from supermarket chains and open-air markets in Hefei,16 samples(13.3%)were positive for Salmonella,with the highest contamination rate of 22.2% for chicken.High resistance was observed for ampicillin(87.5%),doxycycline(75.0%),and tetracycline(62.5%).The sul2 was detected in all isolates,and the aac(6')-Ib-cr(93.8%)and the tet A(81.3%)were predominant.Moreover,12 isolates showed multiple antimicrobial resistant phenotypes.Interestingly,all the Salmonella isolates contained the genes mog A,mgt C,sop B,and spv B.(2)The minimum inhibitory concentrations(MICs)of thymol,carvacrol and cinnamaldehyde were 128 ?g/m L,256 ?g/m L and 128 ?g/m L,respectively.Thymol and carvacrol with MIC concentration not only significantly inhibited the growth of Salmonella counts and bacterial counts of chicken at storage(P < 0.05),but also reduced p H,moisture content and total volatile basic nitrogen value,improved color and sensory quality,and extracted the shelf life,while there was no significant difference between cinnamaldehyde treated group with MIC concentration and the control group.(3)Thymol(2MIC),carvacrol(MIC)and cinnamaldehyde(2MIC)significantly reduced the biofilm formation ability with OD values of 0.098,0.098 and 0.178 at 48 h,respectively,enhanced the eradicate ability of mature biofilm(P < 0.05),and inhibited the metabolic ability of bacteria in the biofilm,reducing them by 95.87%,97.4% and 67.65%,respectively.SEM and CLSM images revealed that thymol(2MIC),carvacrol(MIC)and cinnamaldehyde(2MIC)destoryed the biofilm structure and decomposed extracellular polysaccharides,leading to leakage of contents and inactivation of bacterial,which showed thymol,carvacrol and cinnamaldehyde had a good inhibitory effect on biofilm development(formation and dissociation).