Isolation And Identification, Molecular Epidemiological Survey And Pathogenic Research Of Salmonella Pullorum In Eastern China

Salmonella is a kind of very important Zoonotic bacteria, the number of global distributed serotypes has been over2500. Avian Salmonellosis is a variety of acute and chronic diseases caused by one or more member of Salmonella, which presents as septicemia and enteritis in infected animals. S. pullorum is a member of avian Salmonella, and it can infect chicken no matter the breed and age. In our country, Pullorum disease was still one of the infectious diseases which were seriously harmful to poultry husbandry. In this study, Salmonella from poultry were isolated and identified. The serotype, antimicrobial resistance and virulence genes of S. pullorum were analysed; The pathogenicity of two S. pullorum isolates in this study was investigated with histopathology and imrnunohistochemistry. The results may useful to understanding the pathogenesis of Salmonella.1. Idenfication and serotype analysis of avian SalmonellaTo investigate the distribution and the dominant serotype of avian Salmonella in Eastern China. Samples were detected with enrichment, purification, PCR, serotype identification and biochemical identification, and seven S. pullorum isolates with Hd and Hg mutated serotypes were sequenced. The results showed that87isolates were identified as Salmonella and belonged to five subtypes, including S. typhimurium (2/87), S. derby (4/87), S. saintpaul (1/87), S. pullorum (78/87) and S. abaetetuba (2/87). These results indicated that poultry were mainly infected by S. pullorum in Eastern China. The mutation rate of serotype in S. pullorum increased.2. Antimicrobial resistance analysis of S. pullorumAntimicrobial resistance of78S. pullorum isolated from October2010to August2012was determined by antibiotic susceptibility test (KB method). The results showed that, S. pullorum displayed a high antimicrobial resistance, particular against nalidixic acid, carbenicillin, streptomycin, sulfafurazole and ampicillin. While most isolates were sensitive to gentamicin, cefatriaxone, chloromycetin and kanamycin.62isolates exhibited multiple drug resistance.3. Virulence gene analysis of S. pullorumTo investigate Salmonella pathogenicity island (SPI) in.S. pullorum isolated in the study, the virulence genes hilA, sseL, mgtC, siiE and sopB were detected by PCR in78S. pullorum. Furthermore, the virulence genes of10isolates from different species were sequenced. The results showed that three virulence genes hilA, sseL and mgtC locating in SPI-1, SPI-2and SPI-3respectively, were highly homo logous(100%) to the strains in GenBank, but a few mutations occurred in siiE and sopB genes locating in SPI-4and SPI-5of3isolates.4. The pathogenicity of S. pullorumThe pathogencity of S. Pullorum was determined in the experiments. Fatal infection experiment was conducted in young chickens by inoculating12S. Pullorum. LD50of2isolates from the12S. Pullorum was calculated by infecting1-day-old chicken, as well as bacterial distribution and pathological lesion at the different time point during infection. S. Pullorum was isolated in organs at day3after inoculation; The most serious lesion appeared during day7-14, while it decreased significantly after day21. The quantity of S. Pullorum varied in different organs during infection.