Headspace gas chromatographic method for antimicrobial screening: Minimum inhibitory concentration determination

Abstract

The headspace gas chromatographic method has been widely used to detect volatile metabolites to reflect the growth state of microorganisms, however, it has never been used for the determination of the minimum inhibitory concentration in antibacterial drugs. This paper reports a new method for evaluating the antimicrobial activity of drugs by measuring the amount of CO2 produced by bacterial metabolism after treatment with drugs. According to the amount of CO2 produced by bacterial metabolism, a proper amount of bacterial liquid is selected and added to a drug-containing culture medium as compared with bacteria without drugs in parallel. The amount of CO2 produced by bacteria is measured by using a headspace gas chromatograph coupled with a thermal conductivity detector to measure the bacteriostasis rate and the minimum bacteriostasis concentration of the tested drug, so as to evaluate its antibacterial activity. The accuracy of this method was verified by comparison with the standard method (the OD method), which indicated that the precision was less than 3 % (expressed by relative standard deviation), the inhibition rate (R2 = 0.968) was consistent with the reference method above. This method is simple in operation and can avoid the error caused by the properties of the sample such as volatility, solubility and color in the determination of the minimum inhibitory concentration. It is suitable for the determination of antibacterial activity of drugs, especially natural drugs.