| Escherichia coli,one of the common pathogens in poultry production,can cause acute sepsis or inflammation of multiple tissues and organs in poultry,which disease would bring great losses to poultry farmers.The antibiotics are most drugs for treatment of clinical avian colibacillosis,however,the method faces new challenges in recent years.The emergence of "super bacteria" has made more and more people realize the side effects of antibiotic treatment,i.e.expanded drug resistance spectrum of bacteria.Firstly,drug resistance reduces the effect of antibacterial treatment.Secondly,dose increases of antibiotics result in drug residue in poultry,which is harmful to human health and poses a threat to public health and safety.In recent years,with the advent of "the era of no antibiotics",Chinese herbal medicine has been paid more attention,and more and more researchers begin to pay attention to the role of Chinese herbal medicine in the prevention and treatment of bacterial diseases.In the prevention and control of avian colibacillosis,Chinese herbal medicine and its compound preparation have better curative effect,especially Chinese medicinal herbs:Coptis,Scutellaria baicalensis and honeysuckle,which have obvious effect on inhibiting and killing Escherichia coli.Since the use of Chinese herbal medicine produces less residues,it is not easy to produce drug resistance and has little impact on the quality of livestock and poultry products,which can better meet the needs of users,and satisfy the requirements of China’s ecological and green breeding industry,and has broad application prospects.In this study,based on the establishment of artificial infection model of avian colibacillosis in the laboratory,and the previous researches on the prevention and control of avian colibacillosis by Chinese herbal medicine,we conducted the selection,improvement and curative effect test of the classic Chinese herbal medicine "Gegen Qinlian Decoction".This study will provide new ideas for the prevention and control of avian colibacillosis.1.Optimization of the ingredients for "Gegen Qinlian Decoction"The mice model of E.coli infection was established by intraperitoneal injection of different concentrations of E.coli;on the basis of previous studies on the prevention and control of colibacillosis by Chinese herbal medicine,five prescriptions were formed through the improvement of the classic Chinese herbal medicine prescription "Gegen Qinlian Decoction";the therapeutic effects of different groups were evaluated by three times of administration at 1 h,6 h and 12 h after Ecoli challenge.The results showed that all mice were infected and died rapidly within 24-48 h after intraperitoneal challenge with 0.5 mL bacterial suspension including 9.75×108 CFU/mL.This challege dose was selected as optimal dose for the mousr infection model.After challenge,the cure rate of formula I(honeysuckle,Pueraria,Scutellaria,Coptis,Paeonia lactiflora and roasted licorice)was 70%,which was the highest cure rate among the three formulas,and no administration bacterial strain was isolated from liver and heart tissue of infected mice.Therefore,formula 1 was selected for the further study in chicken colibacillosis model.2.Therapeutic effect of improved formula of "Gegen Qinlian Decoction" on artificially induced chicken colibacillosisTo establish a chicken infection model of E.col,chickens were intramuscularly injected with different concentrations of E.coli,and the morbidity and mortality of infected chickens were observed.The infected chickens were administered with high dose(1.5 ml/kg body weight),medium dose(1.0 ml/kg body weight)and low dose(0.5 ml/kg body weight)of the improved "Gegen Qinlian Decoction" in drinking water for 5 continuous days when their symptoms appeared,while florfenicol treatment was used as control,and the drug treatment effect was evaluated accordingly.The results showed that 10-4 dilution of the bacterial culture medium(0.5ml)was selected as the administration dose based on the half deaths of the infected chickens.The high dose and medium dose treatment groups of the improved "Gegen Qinlian Decoction" had significant curative effect on chicken Colibacillosis,which was equivalent to florfenicol.Since there was no significant difference in each index between high and medium dose treament groups,and medium dose of "Gegen Qinlian Decoction" was selected as recommendation dose. |
