Rapid monitoring of microbial contamination on herbal medicines by fluorescent staining method

AIMS: To apply fluorescent staining method for fast assessment of microbial quality of herbal medicines. METHODS AND RESULTS: The number of total bacteria and esterase-active bacteria on powdered traditional Chinese medicines were enumerated by fluorescent staining method using 6-carboxyfluorescein diacetate (6CFDA) and 4',6-diamidino-2-phenylindole (DAPI), and they were compared with colony-forming units (CFU). The CFU was approximately 10(3) per gram in ginseng radix, and no bacterial colonies were detected from others. However, the total bacterial number (TDC) was more than 10(7) per gram, and number of bacteria possessing esterase activity ranged from 1 to 3% of TDC. CONCLUSIONS, SIGNIFICANCE AND IMPACT OF THE STUDY: Many bacteria in each Chinese medicine had enzyme activity and most of them could not be detected by conventional plate counting technique. Enumeration of bacterial cells on traditional Chinese medicines by fluorescent staining method requires less than 1 h. The double staining method with 6CFDA and DAPI could be applicable to rapid microbial monitoring of crude drugs.