Isolation And Identification Of Salmonella In Egg And The Detection Of Its Resistance Genes And Virulence Genes

Salmonella infection is one of the sciences of public health significance of zoonoticdisease. Chicken is the most important host of Salmonella, any type of Salmonella can causethe chicken acute or chronic diseases. Chickens infected with Salmonella can also infect eggswhich cause vertical transmission of salmonella, thus it creates a vicious cycle. When theflock of Salmonella infection outbreaks,80%chickens will die, causing huge economiclosses to the poultry industry. Once the intake of animal foods contains a large number ofSalmonella, it can cause foodborne poisoning. Based on statistics,70％～80％of the bacterialfood poisonings were due to Salmonella in China. As the most common source of pollution ofthe eggs, salmonella has become an important foodborne micro-organism. Therefore, thedetection of Salmonella in eggs was of great significance in Food Safety and Public Health．1.1200egg were collected in the hatchery from6different cities in Shaanxi Province,under sterile conditions, the eggshell membranes were collected and cultured, using themethod of Salmonella enrichment medium for isolating and identify Salmonella strains. Thebacteriology conventional separation techniques, biochemical tests and immunological testswere needed. The result shows that60Salmonella strains were isolated, and the rate for theisolation was5.0%.2. According to the sequence of drug resistance genes published by GenBank, whichdesigned13pairs of the PCR primers to enlarge and detect the drug resistance genes,7kindsof drug resistance genes were detected, where the carried rate of flor were100%andBlaCMY-2were higher than60%. The drug sensitivity test shows that the60isolated strainshave high resistance rate to trimethoprim, cephalosporins, nalidixic acid, ciprofloxacin,chloramphenicol, kanamycin and tetracycline, but the resistance rate was lower toAmoxicillin, gentamicin, norfloxacin, tobramycin, streptomycin, ofloxacin, cefotaxime,ceftazidime and amikacin. The isolates that resistant to more than3kinds of antimicrobialsaccounted for98.4%. The most severe isolated strainsc can resistant to12kinds ofantimicrobials, but there was no absolute correlation between resistance phenotype and theresistance gene carried.3. According to the animal pathogenesis test, there were14strains that have strong pathogenic among the60Salmonella strains which took a part of23.3%. According to thesequence of SPI genes published by GenBank,5pairs of the PCR primers were designed toenlarge and detect the core protein of the SPI genes.The results show that the carried rate ofthe SPI genes from the isolated strains indicated that SPI-1were60%, SPI-2were73.3%,SPI-3were100%, SPI-4were90%, and that SPI-5were76.7%, then an analysis also hasdone which knows the isolates with the genes of SPI-1and SPI-2have more intimaterelationship between the pathogenesis and the SPI carried. The pathogenic of strains whichcarried SPI-1genes was higher than strains which carried SPI-2genes, but the in carrying ofSPI-4and SPI-5there was no significant correlation between the pathogenesis and the SPIcarried.