Study On Compounds Of Chinese Herbs And Antimicrobials For The Prevention And Treatment Of Chicken Colibacillosis

Chicken colibacillosis is a disease which is caused by Escherichia coli of different serotypes. With the development of poultry industry, situation of the disease is more and more serious, and heavy loss has been caused. In addition, abuse of antimicrobials causes the appearance of multi-drug resistant strain, which makes the prevention and treatment of chicken colibacillosis more difficult.176 strains of Escherichia coli were isolated from 48 chicken farms in Shandong province to investigate their serotypes and resistance susceptibility to antimicrobials. Results showed that among 13 serotypes got in the study, O₇₈,O₁,O₈,O₁₄₃ are predominant, and the percentage of isolation are 13.5%, 7.2%, 3.2% and 3.0%, respectively. Result of antimicrobial disk susceptibility test showed that antimicrobial resistance of bacteria was serious and mainly multi-drug resistance. Most isolates are resistant to more than 9 kinds of antimicrobials. The popularity of antibiotic resistance in Shandong Province indicated the importance of study compound of Chinese herbs and antimicrobials which had better effect and less possibility to cause antimicrobial resistant strains.Minimum inhibitory concentrations (MIC) of ten Chinese herbs and their combinations were determined for Escherichia coli. Sensitivity of E. coli incubated under selective pressure to Chinese herbs as well as to antimicrobials was also studied. Result showed that Scutellaria baicalensis Georgi had a high level of direct activity against Escherichia coli. Combinations of Scutellaria baicalensis Georgi with Forsythia suspense or Taraxacum mongolicum or Fraxinus chinensis showed significant antibacterial action, so did combination of Forsythia suspensa with Fraxinus chinensis. Both Escherichia coli strains incubated on culture with Chinese herbs for 200 generations exhibited no or slight resistance to theses herbs. Further more, the multi-drug resistant strain showed decreased resistance to antimicrobials, while the standard strain remained the same.Scutellaria baicalensis Georgi and four Chinese herb combinations were combined with five kinds of antimicrobials respectively to determine their inhibitory effects on Escherichia coli. The results showed that different combinations differed greatly in inhibitory effect. Combinations of Scutellaria baicalensis Georgi with the five antimicrobials can significantly inhibit the growth of both standard Escherichia coli and resistant Escherichia coli. In addition, sensitivity of standard Escherichia coli and resistant Escherichia coli are different to the same combination.Compound of Chinese herbs and antimicrobials was used to prevent and treat experimental chicken colibacillosis. Result showed that the compound was effective. Further more, in prevention trial, content of Amikacin in compound B is the same as that in Amikacin control group, but compound B is significantly more effective than Amikacin control group;content of Amikacin in compound A is half of that in Amikacin control group, the prophylactic effect is similar. That means dosage of Amikacin can be reduced when using compound A to prevent chicken colibacillosis, and it is good to reduce antimicrobial residue and resistance problem. In all, Scutellaria baicalensis Georgi has synergistic activity with Amikacin.