PLANT CELL BIOTECHNOLOGY AND MOLECULAR BIOLOGY

The antimicrobial effect of extracts of the following combinations – African geranium (Pelargonium sidoides DC.) & black elderberry (Sambucus nigra L.), St. John's wort (Hypericum perforatum L.) & black elderberry (Sambucus nigra L.) and African geranium (Pelargonium sidoides DC.) & St. John's wort (Hypericum perforatum L.)  in colloidal nanosilver (AgNPs) at a concentration of 30 ppm and in water was examined against Esherichia coli ATCC, Salmonella enterica ATCC, Staphylococcus aureus ATCC, Clostridium perfringens ATCC, Candida albicans ATCC and two clinical isolates (Pseudomonas aeruginosa and Streptococcus pyogenes). The classical agar-gel diffusion method, determination of Minimum inhibitory concentrations and suspension tests for determination the time of antimicrobial action of the herbal extracts in AgNPs were used.

Significant antimicrobial effect of aqueous extracts of each of the three tested herbs was found. The addition of AgNPs to each of the extracts resulted in enhanced antimicrobial activity. The combination of the three herbal extracts was synergistic in terms of the antimicrobial effect that increases. Their bactericidal effect was faster in the presence of AgNPs than in the absence of silver. When in a lower density suspension, the tested microorganisms showed a higher sensitivity to the tested herbal extracts. The Gram-negative bacteria tested died in a much shorter time than the Gram-positive ones. In the case of aqueous extracts without silver, the reduction of the tested microorganisms from all groups occurred more slowly than when the herbal combination contained AgNPs. Higher sensitivity to all studied herbs, as well as to the combination between them, showed the studied Gram-negative bacteria compared to Gram-positive microorganisms. The highest sensitivity by this method was found in E. coli and P. aeruginosa, as well as the strict anaerobe Clostridium perfringens. The oval fungus C. albicans also showed sensitivity to all studied herbs.