The Prevalence Of Salmonella And Thermal Resistance In Chicken And Ready-to-eat Meat

Salmonella is one species of zoonotic pathogen and one of important foodborne pathogens.If meat was contaminated by Salmonella,this may lead to serious food safety problems,and become a serious threat to human health.Currently,the distribution in Salmonella which is in ready-to-eat meat is unclear,and research on the thermal resistance of Salmonella has not been reported.Epidemiological distribution of Salmonella in chicken and ready-to-eat meat was studied in this article.Serotypes,virulence-associated genes,PFGE types and thermal resistance were investigated to analyze their resistance and genetic relationship.This research can provide solutions for prevention and control this pathogen,and lay the foundation for the mechanism of heat inactivation.The results showed that:(1)To study the incidence of Salmonella in commercial chicken and ready-to-eat meat,a total of 134 meat products samples were collected from supermarkets and marketplaces;55 samples raw chicken breast,55 samples raw chicken leg and 24 samples ready-to-eat meat.Samples were investigated for the presence of Salmonella spp.by using bacteriological,biochemical tests and PCR assay.It was observed that 44%(11/25)of raw chicken breasts from supermarkets;32%(8/25)of raw chicken legs from supermarkets;30%(9/30)of raw chicken breasts from marketplaces;40%(12/30)of raw chicken legs from marketplaces and 20.8%(5/24)of ready-to-eat meat were positive for salmonella.Seven serovars were identified among the 45 Salmonella isolates.The serovars were Paratyphi-A(n=16),Typhi(n=6),Typhimurium(n=3),Potsdam(n=3),Senftenberg(n=3),Agona(n=6),Aberdeen(n=8).(2)Virulence plasmids genes of 45 Salmonella strains were detected by PCR using primers stn,spvA,spvB,spvC,spvD,spvR,rck.Results:Of 45 isolates,8 Aberdeen,6 Agona and 2 Potsdam from chicken showed presence of all 7 virulence plasmids genes,which were stn,spvA,spvB,spvC,spvD,spvR,rck;16 Paratyphi-A(1 from ready-to-eat meat)showed presence of virulence plasmids genes spvA and stn;I Typhi from chicken showed presence of virulence plasmids genes stn;all isolates of Typhimurium and Senftenberg were not detected the 7 virulence plasmids genes.(3)To investigate the genetic relationship of the Salmonella isolated from people and food,8 Salmonella isolated from food and 5 Salmonella isolated from people were digested by restriction endonuclease Xba I and typed by Pulsed-Field Gel Electrophoresis(PFGE).The electrophoresis profiles were analysis software-Info Quest FP.The results showed that the same serotype Salmonella were not obvious,but the obvious diversity were found in the different serotype.S.agona from food was closely related to S.dublin from people;S.Aberdeen from food was closely related to S.enteritidis.(4)In the study of microbial sterilization,D value was used for the evaluation of heat inactivation rate of isolated Salmenolla in NB and ready-to-eat meat.7 isolated Salmenolla were inoculated and the samples were heated at 63?,68? and 72? respectively.The survival curves of Salmenolla in NB at 68? were fitted with modified Slogistic model.The survival curves of Salmenolla in ready-to-eat meat at 63?,68?,72? were fitted with linear model.D value of 7 isolated Salmenolla were obvious diversity.For the given set of growth conditions,strain S.typhimurium was more heat-resistant than another strains.