Antibacterial Properties of Plant Extracts Used in Traditional Chinese Medicine for Streptococcus pneumoniae and Neisseria gonorrhoeae

Abstract

The overuse of antibiotics has led to multi-drug resistant (MDR) organisms which few antibiotics can kill. Due to the need for novel antibiotics, pharmaceutical developers are looking at ancient homeopathic remedies for answers. The purpose of this study was to determine if any traditional Chinese medicine (TCM) crude extracts had antibacterial properties, with the larger goal of identifying antibacterial drug candidates. A total of 120 extracts from 22 plants used in traditional Chinese medicine (TCM) from Guangxi Botanical Garden of Medicinal Plants (GBGMP) in Nanning, China were assayed against Streptococcus pneumoniae and Neisseria gonorrhoeae. This was done following Clinical Laboratory Standards Institute guidelines for aerobacteria using the broth microdilution assay and the disk diffusion assay, respectively. The broth microdilution assayed revealed the minimum inhibitory concentration (MIC) and the MIC50. Select extracts exhibiting greater than 80% bacterial inhibition and less than 10% toxicity against mammalian cells underwent a dose response to determine the minimum bactericidal concentration (MBC). Of the 120 extracts assayed, none were found to inhibit N. gonorrhoeae. Overall, 28 extracts exhibited inhibition within the above parameters against S. pneumoniae. Three of the extracts had bactericidal potential, 21 had bacteriostatic potential, and four extracts had confounding results and need to be retested. Further testing is needed to identify pure compounds from the crude extracts.