Abstract: To study the antibacterial effect in vitro of Andrographis aqueous extract associated with clinical commonly used 10 kinds of antimicrobial agents to the chicken pathogenic Escherichia coli. Andrographis prepared by the traditional water extraction liquid and concentrated to a concentration of 1 g/mL, determined the in vitro inhibitory effect of Andrographis aqueous extract respectively, associated with amoxicillin, ceftriaxone, and other 10 kinds of commonly used clinical antimicrobial drugs, using the agar dilution method, to the clinical 10 chicken pathogenic Escherichia coli. The results show that Andrographis paniculata and ceftriaxone, Andrographis paniculata and florfenicol associated with 100% showing a synergistic effect; Andrographis paniculata and ceftiofur associated with 90% showing a synergistic effect, 10% showing unrelated; Andrographis paniculata and spectinomycin combined with 80% showing synergies, 20% showing unrelated; Andrographis paniculata and lincomycin associated with 50% showing a synergistic effect, 40% for unrelated or antagonistic effects, of 10% for unrelated; Andrographis paniculata with amoxicillin, apramycin, amikacin, doxycycline, enrofloxacin linked to unrelated or antagonistic effects mainly. The above results revealed that, in vitro, Andrographis paniculata associated with ceftriaxone, ceftiofur, spectinomycin, florfenicol showing synergy to chicken pathogenic Escherichia coli, with amoxicillin, apramycin, amikacin,lincomycin, doxycycline, enrofloxacin with unrelated or antagonistic effects.

Key words: Andrographis paniculata; antimicrobial agents; used combination with; chicken pathogenic Escherichia coli; antibacterial activity in vitro