| Salmonella has been well known around the world due to its ability of causing many food-borne illnesses. Salmonellosis can not only cause pig infections, but also be the risk of transmitting the pathogen bacteria in the environment.Contaminated pork products are the major sources of foodborne illness. Salmonellae serovars could survive in the environment for a long time. Since Pig industry is an important industry in Guangxi, it is important to study on the identification and biological characteristics of Salmonella isolates from pig origin in Guangxi province. In order to provide the theoretical basis for controlling Salmonellae in pig productio, The study includes four parts:1. Identification and serotype determination of the Salmonella isolates from pig’s feces and raw pork.287feces samples of healthy pigs were collected from several pig farms of three different regions in Guangxi. Salmonellae were isolated and identified according to the National food safety standard Food microbiological examination:Salmonella (GB4789.4-2010).Further identification was carried out with PCR identifications of the invA gene. The result showed that six Salmonella strains from feces were isolated, the average separation rate was2.09%. A total of174raw pork from12markets of Nanning were collected and Salmonellae were isolated and identified.20Salmonella strains from raw pork were identified, the rate for the isolation was11.49%. By slide agglutination, the isolates from feces belongs to the B, E1, C1and C2serum groups and the isolates from raw pork belongs to the B, E1, C2serum groups. The B group is the most primary serogroup. S. Derby and S.typhimurium were the most primary prevalence serotypes of Salmonella in feces, while S. Derby was the most primary prevalence serotype in raw pork.2. Pathogenicity and virulence genes detection of the Salmonella isolates.The results of the mice pathogenesis test showed out:Six Salmonella strains in feces were classed as strong pathogenic(4strains,66.67%), medium pathogenic(1strains,16.67%) and weak (1strain,16.67%);20Salmonella isolates from raw pork were classed as strong(13strains,65%),medium(4strains,20%) and no virulence(3strains,15%).According to the five virulence genes(mogA、ssel、 mgtC、siiE、sopB) detection results, The gene detection rate of39Salmonella strains from pig feces were89.74%(mogA\SPI1),100.00%(ssel\SPI2),100.00%(mgtC\SPI3),92.31%(siiE\SPI4),1000.00%(sopB\SPI5) respectively. The gene detection rate of20Salmonella strains from raw pork were85.00%(mogA\SPI1),100.00%(ssel\SPI2),100.00%(mgtC\SPI3),65.00%(siiE\SP I4),90.00%(sopB\SPI5). The results indicated that all of the Salmonella isolates have no absence for SPI2and SPI3genes. It is found out that there were more intimate relationship between the pathogenesis and the SPI1. Among the seven strains without SPI1gene, two were medium virulence, one was weak and four strains had no virulence. The Salmonella isolates from raw pork have higher rate of lacking for SPI4and SPI5than these from pig feces.3. Antimicrobial susceptibility testing and drug-resistance genes detection of the Salmonella isolates.26isolates were examined for susceptibility to25antimicrobial agents.The results indicated that all of the isolates exhibited different resistance to several antibiotics. Six strains from pig feces showed resistance to10antibiotics on average and20strains from raw pork exhibited resistance to four antibiotics. Salmonella isolates from pig feces had much more widely resistance spectrum than those from raw pork.The6isolates from2011to2012from pig feces(on an average of9kinds of antibiotic resistance) drug-resistant bacteria spectrum broadening than the33isolates from2010to2011from pig feces(on an average of7kinds of antibiotic resistance)All of the salmonella strains were severe resistance to penicillin, tetracycline, sulfa, benzene, whereas sensitive to lactam enzymes, fluoroquinolone, quinolone, nitro furans, aminoglycoside. According to the results of the strains from pig feces, the relation between the drug resistance phenotypes and the drug-resistance genes (quinolone, amine, beta phthalein enzymes, aminoglycoside, sulfa, chloramphenicol and tetracycline)detection were from83.33%to100.00%.14resistance genes were detected on average. The detecting rates of sul1and cmlA were100%. According to the results of the strains from raw pork, the relation between the drug resistance phenotypes and the drug-resistance genes (quinolone, amine, beta phthalein enzymes, aminoglycoside, sulfa, chloramphenicol and tetracycline) detection were from50.00%to100.00%. Six drug-resistance genes were detected on average and gene detection rate were from5.00%to75.00%,with the detection rate of cmlA and tetA were75.00%.It has a lot of relationships between resistant phenotype and drug-resistant genes.6isolates from pig feces intIl gene detection rate of were100.00%, while20isolates from raw pork detection rate of were25.00%.We can not detect the intI2gene and intI3gene.IntIl gene have close relationship with multiple drug-resistant.4. Biofilm formation of the the Salmonella isolates.59Salmonella Isolates were classified as NOT (13strains,20.3%),weak (20strains,33.9%), moderate (6strains,10.17%)or strong (20strains,33.9%) biofilm producers.79.64%of the total number of strains have adhesion abilities.75.00%of the S.typhimurium strains were strong biofilm producers, whereas17.39%of S.Derby strains had adhesive ability.38strains(97.44%) from pig feces have biofilm-forming abilities, while9strains (45%)from raw pork showed adhesive abilities.11S. Derby Isolates from pig feces all of that had adhesive ability,and4strains(33.9%)were classified as strong biofilm producers. While only5strains(41.67%) that from12S. Derby Isolates which from raw pork had adhesive ability,including weak adhesion strains(4strains) and medium adhesion strains(1strains). So adhesive ability of Salmonella isolates from pig feces ratio higher than Salmonella isolates from raw pork and tend to stronger adhesive ability. The findings suggested that The biofilm formation abilities of the Salmonella isolates were concerned with salmonella serotypes and sources, which deserves further research. |
PDF Full Text Request