| At present,colibacillosis of chicken is an important bacterial infectious disease,causing serious threat to the poultry industry in China.According to the Xinyang Animal Disease Inspection Center(Municipal Engineering Center of Xinyang Agriculture and Forestry University)on the investigation of chickens in concentrated area of south of Henan Province,the incidence rate of colibacillosis has always been in the first place,among the bacterial diseases in large-scale poultry farms.There are many serotypes of avian Escherichia coli,and the resistant strains are also increasing,which makes it difficult to prevent and cure the disease.Therefore,It has important theoretic and practical significance to carry out Etiological investigation and analysis of colibacillosis in chickens in southern Henan Province for the effective prevention and treatment of colibacillosis of chickens.This study relates to the isolation and identification of chicken pathogenic Escherichia coli in southern region of Hennan province,the analysis of common antibacterial resistance of isolated strains,the combined antibacterial action of active components of Chinese medicine and aminoglycosides in vitro,and using the advantages of pathogenic strains developed polyvalent inactivated vaccine and so on.Through the series of researches,the epidemic status of chicken colibacillosis in southern Henan province were understood.It will provide an important theoretical basis and clinical value for the scientific prevention and control of chicken colibacillosis in the south of Henan Province and Henan Province.1 The isolation and identification of chicken pathogenic Escherichia coli in southern region of Hennan provinceThrough the conventional method of cultivation,purification,microscopic examination,physiological and biochemical identification and PCR identification,121 strains of Escherichia coli were isolated from 164 sick chicken samples for inspection in southern Henan area.Among these Escherichia coli isolates,88 were determined to be placed in serogroups.These isolates included 17 serogroups,and 72(59.50%)of them belonged to O2,O78,O1,O18,O26,O22.The pathogenicities of 121 Escherichia coli strains were evaluated in chickens,and the visible symptoms and pathological changes of Challenged Chicken were consistent with the characteristics of colibacillosis;among them,52.9%(64/121),25.6%(31/121),21.5%(31/121)were characterized as high,intermediate and low in pathogenicity,respectively.2 The analysis of antimicrobial resistance of the Escherichia coli isolatesThe minimal inhibitory concentration(MIC)of 62 strains of Escherichia coli against 18 kinds drugs in vitro were determined by standard microdilution method,and class I integrase gene was amplified by PCR.The results showed that all strains showed multiple drug resistance,drug resistance pattern is up to more than 12 kinds of antibacterial drugs;62 isolates all showed different degrees of resistance to beta-lactams,amphenicols,aminoglycosides,quinolones,sulfonamides,tetracyclines;the drug resistance rates of the isolates to terramycin,sulfamethoxazole,sulfadiazine,doxycycline were 95.2%,87.1%,80.6%,72.6%,respectively;the class I integrase gene positive rate was 87.1%.The results showed that the clinical isolates of avian Escherichia coli had varying degrees of resistance to commonly used antimicrobial.3 the combined antibacterial action of active components of Chinese medicine and aminoglycosides in vitroCheckerboard dilution method was used to study the combined antibacterial action of active components of Chinese medicine and aminoglycosides in vitro,and then to screen the drugs with synergistic antibacterial effect,which provided a theoretical basis for study in vivo.The results showed that andrographolide and aminoglycoside drugs mainly had synergistic effect;baicalin and berberine respectively combining with aminoglycosides mainly had additive effects;dandelion extract and aminoglycoside drugs mainly had independent action.Therefore,the combination of andrographolide and aminoglycosides can improve the antibacterial effect against Escherichia coli.4 Preparation and evaluation of polyvalent inactivated vaccine of avian Escherichia coliThe isolates of Escherichia coli with high toxicity,good immunogenicity and local representative serotype(O1、O2,O78,O22,O26 and O18)were prepared polyvalent inactivated vaccine.The result of immune challenge test showed that the vaccine was safe for chickens of all ages.and the group was protected by Escherichia coli strain,which indicated that the vaccine was effective in the treatment.The groups of immune chickens challenged by the isolates of Escherichia coli were full protection,which indicated that the vaccine was effective again colibacillosis of chickens.These achievements had an important guiding significance for effectively preventing and controlling colibacillosis in chickens and improving the whole chicken raising level in the south of Henan province. |
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