Screening of plant extracts for antimicrobial activity against bacteria and yeasts with dermatological relevance.

Abstract There is cumulative resistance against antibiotics of many bacteria. Therefore, the development of new antiseptics and antimicrobial agents for the treatment of skin infections is of increasing interest. We have screened six plant extracts and isolated compounds for antimicrobial effects on bacteria and yeasts with dermatological relevance. The following plant extracts have been tested: Gentiana lutea, Harpagophytum procumbens, Boswellia serrata (dry extracts), Usnea barbata, Rosmarinus officinalis and Salvia officinalis (supercritical carbon dioxide [CO 2 ] extracts). Additionally, the following characteristic plant substances were tested: usnic acid, carnosol, carnosic acid, ursolic acid, oleanolic acid, harpagoside, boswellic acid and gentiopicroside. The extracts and compounds were tested against 29 aerobic and anaerobic bacteria and yeasts in the agar dilution test. U. barbata-extract and usnic acid were the most active compounds, especially in anaerobic bacteria. Usnea CO 2 -extract effectively inhibited the growth of several Grampositive bacteria like Staphylococcus aureus (including methicillin-resistant strains -MRSA), Propionibacterium acnes and Corynebacterium species. Growth of the dimorphic yeast Malassezia furfur was also inhibited by Usnea-extract. Besides the Usnea-extract, Rosmarinus-, Salvia-, Boswellia-and Harpagophytum-extracts proved to be effective against a panel of bacteria. It is concluded that due to their antimicrobial effects some of the plant extracts may be used for the topical treatment of skin disorders like acne vulgaris and seborrhoic eczema.

Differential T cell responses to Plasmodium chabaudi chabaudi in peripheral blood and spleens of C57BL/6 mice during infection.

Abstract The definition of the immune status of a person is often taken as the responses obtained from lymphocytes isolated from peripheral blood. We therefore analyzed in a mouse model of Plasmodium chabaudi chabaudi the response of T lymphocytes taken from peripheral blood and compared it with the spleen during and after a primary erythrocytic infection. Using limiting dilution conditions, no malaria-specific T cell responses could be measured in the peripheral blood for up to 21 days after infection with P. chabaudi, whereas T cells responding to malaria Ag were readily detected in the spleen. This was true for T cells providing help and for those producing IFN-gamma. After clearance of the parasitemias to subpatent levels (75 days), qualitatively similar T cell responses were found in both compartments of the immune system, i.e., the Th cell response predominated over the inflammatory response. These data suggest that during an active infection with Plasmodium, T cell responses in peripheral blood are not necessarily indicators of the immune status.</jats:p

Role of gamma interferon during infection with Plasmodium chabaudi chabaudi

A role has been proposed for inflammatory mediators such as gamma interferon (IFN-gamma) and reactive oxygen intermediates in the control of the blood stages of Plasmodium organisms. It was previously shown that IFN-gamma can be detected in the plasma of mice with a primary infection by Plasmodium chabaudi chabaudi (AS). We found that susceptible and other resistant mouse strains produced IFN-gamma, suggesting that susceptibility is not due to a defect in IFN-gamma production. Administration of IFN-gamma to intact C57BL/6 mice slightly decreased and partially delayed parasitemia, whereas in vivo depletion of IFN-gamma through injection of a "cocktail" of monoclonal antibodies against IFN-gamma exacerbated infection. Since CD4+ T cells are essential for the development of a protective immune response to P. chabaudi chabaudi, we tested whether CD4+ T cells are responsible for IFN-gamma production in vivo and whether exogenous IFN-gamma can replace the protective function of the CD4+ T cells. Mice depleted of CD4+ T cells were unable to produce IFN-gamma, but factors in addition to IFN-gamma may be important in parasite clearance.</jats:p