Antibacterial activity of herbal infusions against Staphylococcus aureus, Staphylococcus epidermidis and Pseudomonas aeruginosa in vitro

The objective of the study was to determine the antibacterial action of herbal infusions against reference strains of Staphylococcus aureus ATCC 25923, Staphylococcus epidermidis ATCC 14990 and Pseudomonas aeruginosa 27/99 in vitro. The antibacterial activity of herbal infusions was determined using the agar diffusion test. From the culture of reference strains of S. aureus, S. epidermidis and P. aeruginosa, we prepared a suspension of 1.5x10(8) CFU to match 0.5 McFar-land turbidity standard, defined with a densitometer. The obtained suspension was sieved onto Mueller-Hinton agar (Himedia), followed by further cultivation over 24 hours. The inoculations were covered with discs, which were impregnated with corresponding herbal infusions. For positive control, benzylpenicillin sodium salt was used against staphylococci, while in case of P. aeruginosa, gentamicin sulfate was used. S. aureus was most strongly inhibited by Siberian ginseng (Eleutherococcus senticosus, 1.46 times stronger compared to the control), Fiveleaf Aralia (E. sieboldianus, 1.61) and weeping fig (Ficus benjamina, 1.35). In case of S. epidermidis, pomegranate (Punica granatum) showed antibacterial activity (3.53), while P. aeruginosa was inhibited by common yucca (Yucca filamentosa, 1.10), alpenrose (Rhododendron ferrugineum, 1.00), carob (Ceratonia siliqua, 1.21), fenugreek (Trigonella foenum-graecum, 0.97), pomegranate (5.46) and Norway spruce (Picea abies, 1.51). These herbal extracts could be recommended for use against polyresistant strains of the abovementioned microorganisms. The present study showed that the abovementioned species of plants affect polyresistant bacteria strains more intensively than benzylpenicillin sodium salt.