Screen of Chinese herbal medicines originated in Yunnan province against drug resistant, Escherichia coli producing ESBLs in vitro.

Objective:To assay the bacteriostatic activity of the extracts in vitro from ten Chinese herbal medicines against drug resistant Escherichia coli producing extended-spectrum β-lactamase(ESBLs) and to compare their bacteriostasis on drug resistant Escherichia coli strains isolated clinically.Methods:Three Escherichia coli strains were obtained by routine isolation,cultivation and purification of sputum specimens from patients with respiratory diseases.After the extracts from ten Chinese herbal medicines were obtained by using 80% ethanol,agar diffusion method,twofold dilution method were adopted to evaluate their antibacterial activity.Results:Among ten Chinese herbal medicines tested,nine extracts showed different bacteriostatic activity to some extent.Their inhibitory zone diameter(IZD) was 11.0～21.0 mm and their MIC ranged between 0.78 and 12.50 mg/ml against Escherichia coli.The most active extract was from Macleaya cordata(Willd.) R.Br.with IZD at 16 mm and MIC at 1.56 mg/ml.The bacteriostasis of these extracts on standard Escherichia coli was slightly better than those on the drug resistant strain producing ESBLs.Conclusion:Nine of ten tested Chinese herbal medicines demonstrate the bacteriostasis.The extracts with higher bacteriostatic activity against standard Escherichia coli also show higher bacteriostatic activity against drug resistant one.