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Ethanolic extracts and some fractions from 10 Indian medicinal plants, known for antibacterial activity, were investigated for their ability to inhibit clinical isolates of beta-lactamase producing methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-sensitive S. aureus (MSSA). Synergistic interaction of plant extracts with certain antibiotics was also evaluated. The MRSA test strains were found to be multi-drug resistant and also exhibited high level of resistance to common beta-lactam antibiotics. These strains produced beta-lactamases, which hydrolyze one or other beta-lactam antibiotics, tested. The extract of the plants from Camellia sinensis (leaves), Delonix regia (flowers), Holarrhena antidysenterica (bark), Lawsonia inermis (leaves), Punica granatum (rind), Terminalia chebula (fruits) and Terminalia belerica (fruits) showed a broad-spectrum of antibacterial activity with an inhibition zone size of 11 mm to 27 mm, against all the test bacteria. The extracts from the leaves of Ocimum sanctum showed better activity against the three MRSA strains. On the other hand, extracts from Allium sativum (bulb) and Citrus sinensis (rind) exhibited little or no activity, against MRSA strains. The antibacterial potency of crude extracts was determined in terms of minimum inhibitory concentration (MIC) by the tube dilution method. MIC values, of the plant extracts, ranged from 1.3 to 8.2 mg/ml, against the test bacteria. Further, the extracts from Punica granatum and Delonix regia were fractionated in benzene, acetone and methanol. Antibacterial activity was observed in acetone as well as in the methanol fractions. In vitro synergistic interaction of crude extracts from Camellia sinensis, Lawsonia inermis, Punica granatum, Terminalia chebula and Terminalia belerica was detected with tetracycline. Moreover, the extract from Camellia sinensis also showed synergism with ampicillin.TLC of the above extracts revealed the presence of major phytocompounds, like alkaloids, glycosides, flavonoids, phenols and saponins. TLC-bioautography indicated phenols and flavonoids as major active compounds.

Anti-methicillin-resistant Staphylococcus aureus (MRSA) activity of ethanolic extracts of four medicinal plants namely Acorus calamus (rhizome) Hemidesmus indicus (stem), Holarrhena antidysenterica (bark), and Plumbago zeylanica (root), were detected with inhibition zone size ranged from 11 to 44 mm and minimum inhibitory concentration (MIC) varied from 0.32 to 3.25 mg/mL. Further, ethyl acetate, acetone and methanol fractions of above plants demonstrated antibacterial activity. The potency of these fractions based on zone of inhibition and MIC value was relatively higher in P. zeylanica (ethylacetate fraction), followed by acetone fractions of H. indicus, A. calamus, and H. antidysenterica. Time kill assay with most promising fractions of these plant extracts, demonstrated concentration-dependent killing of MRSA within 9-12 h of incubation. Interestingly, synergistic interaction among alcoholic extracts and some fractions of above four plants was evident against MRSA. Further, synergistic interaction of these extracts was detected with one or more antibiotics tested (tetracycline, chloramphenicol, ciprofloxacin, cefuroxime and ceftidizime). The findings also validate the traditional uses of above plants against infectious diseases. Phytochemical studies demonstrated flavonoids and phenols as major active constituents. Further investigations are needed to characterize the active principle and its interaction mechanism with antibiotics.

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In the majority of bacterial and viral infections the generation of cytotoxic T cells is of particular interest because such pathogens are able to escape the host defence mechanisms by surviving intracellularly within the phagocytic cells. To generate a CD8 1 T lymphocyte response against exogenous antigens, the prerequisite is their delivery into the cytosol followed by processing and presentation along with class I major histocompatibility complex (MHC-I) molecules. In the present study we describe the method of liposome-based delivery of antigens and other macromolecules into the cytosol of target cells. To develop safe and effective methods for generating CD8 1 T lymphocytes, we exploited the fusogenic character of lipids derived from lower organisms, that is baker's yeast (Saccharomyces cerevisiae). The degree of fusion with model membrane systems using yeast lipid liposomes varied from 40±70%, as opposed to 1±8% observed with egg PtdCho liposomes, depending on the assay system used. The fusion of yeast lipid liposomes with macrophages resulted in effective delivery of the entrapped solutes into the cytoplasmic compartment. This was further supported by the inhibition of cellular protein synthesis in J774 A1 cells by ricin A, encapsulated in the yeast lipid liposomes. Interestingly, the model antigen ovalbumin, when entrapped in the yeast lipid liposomes, successfully elicited antigen reactive CD8 1 T cell responses. It may be concluded that the liposomes made of lipids derived from S. cerevisiae can spontaneously fuse with macrophages, delivering a significant portion of their contents into the cytoplasmic compartment of the cells.