Evaluation of microbiological quality of medicinal plants used in natural infusions

Consumption of preparations of medicinal plants has been increasing during the last decades in occidental societies. However, there are no effective sanitary controls of these products. To evaluate the nature and content of microbiological contamination, 62 samples of seven medicinal plants (chamomile, leaves of orange tree, flowers of linden, corn silk, marine alga, pennyroyal mint and garden sage) were studied, using conventional microbiological methods. Practically all samples (96.8%) were contaminated with Bacillus cereus; 19.2% of them with levels higher than 10(3) spores/g. The highest levels were found in corn silk samples (> 10(7) spores/g). Spores of Clostridium perfringens were detected in 83.9% of samples, but only 19.2% had levels greater than 10(3)/g. The mean level of fungal population was 10(5.5) cfu/g. Corn silk samples were the most contaminated, with levels above 10(6) cfu/g. Fusarium spp., Penicillium spp., Aspergillus flavus and Asp. niger were predominant in all samples with the exception of garden sage samples. Many yeasts were found in chamomile, flowers of linden, corn silk, pennyroyal mint and garden sage. Predominant species were Cryptococcus laurentii (28.1%) and Rhodotorula mucilaginosa (22.8%). The mean level of Crypt. laurentii contamination in corn silk was greater than 10(4) cfu/g.