The Effect of Vitis vinifera L. Leaves Extract on Leishmania infantum.

Vitis vinifera L.is a traditional Asian herb widely used for different health problems. In the present research, the ethanolic and the aqueous extracts of Vitis vinifera L. leaves collected from shrub, grown in Tunisia, were prepared and evaluated for the antileishmanial activity against Leishmani ainfantum promastigotes. The inhibitory concentration 50 (IC50) was determined and the results showed that the etahnolic extract is more active than the aqueous one (IC50= 0.108 mg/mL). Microscopic observations showed that the ethanolic extract promoted the destruction of cytoplasmic and nuclear membranes of Leishmani ainfantum promastigotes and altered the overall shape of the cell. In order to explain the difference of antileishmanial activity between ethanolic and aqueous extracts, anthocyanins amount was determined by spectrophotometry. It was found that the ethanolic extract is richer in anthocyanins than the aqueous one which can explain the higher antileishmanial activity of the ethanolic extract.

Screening of antileishmanial activity from marine sponge extracts collected off the Tunisian coast.

The present study reports on the in vitro antileishmanial activity of two Ircinidae (Dictyoceratida, Demospongiae, Porifera) Ircinia spinosula and Sarcotragus sp. Sampled from the east coast of Tunisia. The ethyl acetate, dichloromethane, and aqueous extracts were tested against Leishmania major promastigotes. The anti-proliferative activity was checked using different extracts concentration during 72 h. We found that the IC50 (sub-inhibitory concentration) values ranged from 1.39 to 264.67 mug/ml. The most active extract was that from sarcotragus sp dichloromethane extract. Microscopic observations showed that the extracts promoted cellular alterations and induce enlargement of the nucleus and modification of the parasite shape. These promising results in relation with in vitro antileishmanial activity open the way for complementary investigation in order to purify and identify active molecules.

Investigation of several virulence properties among Vibrio alginolyticus strains isolated from diseased cultured fish in Tunisia.

We analysed 34 Vibrio alginolyticus strains isolated from gilthead sea bream Sparus aurata L. and sea bass Dicentrarchus labrax L. cultured in fish farms on the Tunisian Mediterranean coast for the presence of several virulence properties such as extracellular products (ECP) production, growth in iron-limiting conditions and survival in fish serum. The results obtained with different substrates showed that ECP of V. alginolyticus were hydrolytic. The virulence was correlated with the ability of strains to grow in the presence of non-immune fish serum or under conditions of iron limitation. We further examined the presence of virulence genes homologous to those in V. cholerae (toxR, toxS, VPI and ace); toxR was found in 16 V. alginolyticus strains and toxS in 17 strains out of 34 analysed. A positive amplification for the virulence pathogenicity island (VPI) was produced by 12 V alginolyticus strains. Finally, the ace expected amplification fragment was found in 7 V. alginolyticus isolates. Thus, the pathogenicity of V. alginolyticus may be the result of a combination of all these factors.

Survival of Vibrio alginolyticus in seawater and retention of virulence of its starved cells.

The aim of this study was to evaluate the survival responses of four strains of Vibrio alginolyticus in seawater under starvation conditions. We used microcosms containing sterilised seawater and incubated at ambient temperature (22-25 degrees C). V. alginolyticus maintained its culturability for at least nine months. Long-term-starved cells showed an absence or a decrease in their enzymatic activities. Resuscitation assays of viable but non-culturable (VBNC) cells were conducted and the recovery of these cells was achieved after the addition of nutrients. Amplified 16S ribosomal DNA (rDNA) restriction analysis (ARDRA) was used to confirm that the same strain of V. alginolyticus persisted in all microcosms during a long period of time. Starved cells maintained their infectivity for gilt head sea bream (Sparus aurata) and sea bass (Dicentrachus labrax) as determined by intraperitoneal challenges.