The Epidemiological Investigation Of Avian Salmonella In Eastern China And The Preparations Of Microecologics

In recent years,bacterial diseases are becoming more serious and caused huge economic losses in poultry industry with the development of the intensive farms in China.Salmonellosis is particularly important one of these diseases.The overuse of antibiotics and chemical dr?gs causes drug-resistant strains,makes animal disease more difficult to control and treat,and increase the residence of drugs in animal produc,which has a poor effect on food safety,people's health and economic development.Therefore,in order to reduce the application of antibioticsand drug residues,the research of microecologics has become a hot topic.Microecologics is a welcomed biological product in recent years which can not only control and cure disease but also prevent animals from developing disease.Lactobacillus is widely used in microecological preparations at present.Clostridium butyricum has great potential in the preparations of microecologics.It has strong resistance of adverse environment and promoting the growth of Lactobacillus.Adding it to microecological preparations can enhance the stability of viable bacteria.In this study,we evaluated the drug resistance of salmonella stains,screened the strains of Lactobacillus and Clostridium butyricum with high bacteriostasis and tolerability,prepared the microecologics with the best screened strains of lactobacillus and clostridium,and studied its preparation process,evaluated the effect of the self-made microecologics to inhibit salmonella and compared with the commonly used antibiotics in clinical practice.This study provides a new scheme for the prevention and control of salmonella.1.Isolation and identification of Salmonella and analysis of drug resistance in 2016-2017.In 2016-2017,epidemiological investigation was carried out on Salmonella in poultry in East China.A total of 80 Salmonella strains was identified by mPCR and agglutination test,including 27(34.62%)Salmonella pullorum strains,41(52.56%)Salmonella typhimurium strains,10(12.82%)Salmonella enteritidis strains,and 2(2.50%)Salmonella derby strains.Drug sensitivity test showed that 92.31%Salmonella strains were resistant to 6 or more antibiotics,which was especially obvious in ?-lactam Antibiotics.It further confirmed that the muti-drug resistance of strains in East China was very serious.Therefore,it is necessary to study microecologics to deal with this situation.2.Isolation,identification and screening of Lactobacillus and growth characteristics of screened strainsSeventeen starins of probiotics were identified as Lactobacillus salivarius from the 400 faecal samples by 16S rDNA PCR assay,API20A biochemical identification and MBT experiments.The strain of Lctobacillus salivarius TXJ-1 with good performance was screened for the preparation of microecologics.The culture conditions of Lactobacillus salivarius TXJ-1 were optimized.The best culture conditions were grown in medium with pH of 7.0 at 37?,In 200 ml culture volume,the best inoculation amount was 3%,2%glucose(v/w)at was added at 8 h,12 h and 16 h during cultivation process,and pH was adjusted to about 7.0.3 Isolation,identification and screening of Clostridium butyricum and growth characteristics of screened strainsEight Clostridium butyricum starins were identified from the 318 faecal samples by morphology,16SrDNA PCR assay,API20A biochemical identification and MBT experiments.The strains of Clostridium butyricum CYZJ-3 with good performance were screened for the preparations of microecologics.The culture conditions of Clostridium butyricum CYZJ-3 was optimized.The best culture conditions were grew in medium with pH of 6.5 at 38 ?.In 200 ml culture volume,the best inoculation amount was 3%,2%glucose(v/w)at was added at 8 h,12 h and 16 h during cultivation process,and pH was adjusted to about 6.5.4 The preparations and evaluation of compound microecologics.The strain formulation of microecologics was studied.The ratio of 1:1 for Lactobacillus salivarius TXJ-1 and Clostridium butyricum CYZJ-3 had the best bacteriostatic effect,which was confirmed by bacteriostatic test using zone of inhibition and animal experiments.The fermentation process of Lactobacillus salivarius TXJ-1 and Clostridium butyricum CYZJ-3 was optimized.Our results suggested the optimum conditions of Cryoprotectant of Microecologics were as follows:2%glycerine,6%trehalose and 15%skimmed milk.The Average survival rate reached a higher level of 80.5%.Finally,self-made compound microecologics and commonly used florfenicol powder were compared through animal experiments.The self-made microecologics were superior to florfenicol powder in promoting the growth of animals,and similar to florfenicol powder in anti-Salmonella enteritidis.To be more specific,they could effectively prevent Salmonella enteritidis C50041,and significantly reduce diarrhea rate compared with blank control group.In addition,they could optimize the intestinal flora and improve the specific immunity of animals.