Antibacterial Activity of Melissa officinalis , Hypericum perforatum , Sideritis amasiaca and Echinacea sp . Extracts against Some Nosocomial Pathogens

New plant-derived antibacterial agent researches have increased in recent years, because of increased resistance to antimicrobial agents that used against to pathogen microorganisms, and unwanted side effects of food additives. In this study we aimed to determine in vitro antibacterial activity of the extracts of M. officinalis L., S. amasiaca, H. perforatum and Echinacea sp. on some nosocomial bacterial agents. Disc diffusion and broth microdilution tests were used to determine the antibacterial activity of plant extracts on E. coli, K.pneumoniae, P. aeruginosa, methicillin resistance S.aureus (MRSA) and E. faecalis. While, in the disc diffusion test; M. officinalis L. and H. perforatum (8mg/disc) had showed antibacterial activity to all bacteria, S. amasiaca (8mg/disc) had showed antibacterial activity all bacteria exception of E.faecalis, Echinacea sp. (8mg/disc) had showed antibacterial activity only P.aureginosa. MRSA showed the highest sensitivity to all plant extracts with the exception of Echinacea. While, in the broth microdilution test; the values of the minimum inhibitory concentration were between 100 to 1,56 mg/ml for the four plant extracts (200mg/ml). It was observed that all plant extracts caused an inhibitory effect on all the bacteria in different levels (1,56-25mg/ml). In addition, extract of Sideritis amasiaca L. whose antibacterial activity was for the first time investigated and observed against some nosocomial infections agents.