| Salmonella is one of the most important globally-distributed zoonotic pathogens. Until now, more than 2500 serovars of Salmonella enterica have been identified,among which a number of pathogenic serovars can be found in people, livestock and poultry that has caused serious damage to both human health and animal breeding industry.Animal origin Salmonella can widely exist in different animals and animal food, and can spread from animals and food chain to animal and human being. So it is important to study the epidemiology of Salmonella from animal origin. Furthermore, Guangdong is one of the largest poultry and animal products production and consumption province, the supply and safety of animal products directly related to the social stability and the health of the people,but the data of animal origin Salmonella prevalence in Guangdong area are lacking.From May 2015 to December 2015, A total of 415 samples(chicken = 263, pork =128,veterinary hospital =24) were collected from Guangdong province. Two hundred and seventy-three Salmonella strains were isolated. The isolated strains of Salmonella belonged to 28 serotypes; most of them were Salmonella Typhimurium and Salmonella Corvallis,advantages of serotypes of different sample types are distinguished; Isolates were frequently resistant to streptomycin(76.2%), sulfisoxazole(48.0%) and ampicillin(41.4%),51.6% of the strains were resistant to three or more antimicrobial drugs. The isolates were screened for 3 ESBLs genes(bla TEM ? bla CTX-M and bla OXA), 29.3% of the 273 strains analyzed were carried at least one ESBLs gene; 33.7% of the strains were integrase positive via PCR detection, however, only 9.5% of the strains were detected out with gene cassettes.The Salmonella isolates bearing class 1 integron were amplified to six kinds of gene cassettes by DNA sequencing, the number aad A2-dfr A12 were the most frequent, whichindicates that class 1 integron plays an important role in the horizontal transfer of the aminoglycoside antibiotics and sulfonamides resistance genes.In addition, Salmonella enterica serovar Gallinarum biovars Pullorum and Gallinarum are the most common causative agents of chicken salmonellosis resulting in high mortality and morbidity in many parts of the world. It is difficult and laborious to discriminate these diseases via biochemical or phenotypic methods. In this article, we have developed a single nucleotide polymorphism(SNP) PCR-high resolution melt(PCR-HRM) assay for the detection and discrimination of S. Pullorum and S. Gallinarun. The rfb S gene has been identified as good genetic marker for identification of S. Pullorum and S. Gallinarun according to polymorphism at positions 237 and 598. Therefore, PCR-HRM analysis were applied to characterize this gene. The PCR-HRM assay was able to distinguish S. Pullorum,S. Gallinarun and other strains using primer set SP-237F/237 R and SG-598F/598 R. The two assays showed high specificity(100%) for S. Pullorum and S. Gallinarun, and the sensitivity of the two assays was at least 100 times higher than that of the allele-specific PCR assay. The present study demonstrated that HRM analysis confirmed to be a potent,simple and economic tool for rapid, specific and sensitive detection of S. Pullorum and S.Gallinarun.This study provides data supporting for prevention and controling of Salmonella. This is the first report on successful application of the PCR-HRM technology to distinguish S.Pullorum, S. Gallinarum and other strains, and this technique could be applicable in epidemiological research and diagnosis in veterinary clinical laboratory, which can contribute to more timely and efficient control measures on PD or FT. |
PDF Full Text Request