OBJECTIVETo research the bacteriostatic effects of Qingkailing Injection Extract (QKLIE) and combination therapy of Qingkailing Injection (QKLI) and antibiotics on bacteria carrying New Delhi metallo-3-lactamase 1 (NDM-1) blaNDM-1 resistance gene, and to determine their minimal inhibitory concentrations (MIC).

METHODSThe antimicrobial experiments of QKLIE (Radix Isatidis, baicalin, gardenia, honeysuckle) and combination therapy of QKLI and antibiotics were performed by using the agar dilution method and K-B method. The MIC was determined from each extract.

RESULTSThere were different degrees of inhibitory effects on resistant bacteria carrying blaNDM-1 by extracts from main components of QKLI. Of them, the inhibitory effect of baicalin was the best and the MIC of the resistant bacteria was 0.015 g/mL to WD, 0.020 g/mL to WX, 0. 005 g/mL to WJ, and more than 0.020 g/mL to pGEX-4T-NDM-1/DH5alpha (GST-NDM-1), respectively. The MIC value of each extract was sequenced from high to low as baicalin, honeysuckle, gardenia, and Radix Isatidis. Furthermore, combination therapy of QKLI and antibiotics greatly enhanced the antimicrobial activity of each antibiotics when used alone, showing very obvious antibacterial effects on multidrug resistant bacteria carrying blaNDM-1 gene. Of them, the optimal effects were obtained when combined with penicillins (penicillin G, mezlocillin, piperacillin/ tazobactam, ampicillin/sulbactam), with the antibacterial effects improved by 10 folds. The antibacterial effects of other kinds of antibiotics were improved to some extent. Conclusions QKLIE and combination therapy of QKLI and antibiotics showed better bacteriostatic effects on resistant bacteria carrying blaNDM-1 gene. This study provided theoretical bases for drug development, medication and treatment for super-resistant bacteria carrying blaNDM-1.