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Background&Objective: Probiotics have been defined as live microorganisms that confer a health effect on the host when consumed in adequate amounts.Lactic bacteria play an important role in production and maintenance of the fermented and probiotic products.The aim of this study was to determine the efficacy of lactic bacteria, which isolated from yoghurt against Gastrointestinal pathogenic microorganisms in the Golestan province in North of Iran. Materials&Methods: In this descriptive study we used 96 strains which belong to 12 species of Lactobacillus and 5 species of Lactococcus ,that isolated from home made yoghurt, and their antimicrobial effect on 7 species of important intestinal pathogenic microorganisms were examined.After growing the Lactic bacteria in broth media centrifuged and filtred the suspension and used the supernatant for study.The effect of supernatant against intestinal pathogenic microorganisms were assessed by Disc diffusion and pour in well method and each test were repeated 3 times and mean inhibition zone were recorded. Results: Lactobacillus casei and Lactococcus lactis showed better effect than other strains.The maximum light zone diameter was 18 milimeter. Maximum and minimum inhibitiry effect has seen in Yersinia enterocolitica and Bacillus cereus. Conclusion: Both Lactobacillus and Lactococcus strains had a proper inhibitory effect on the intestinal pathogenic bacteria but Lactobacillus strains that present in yoghurt showed better effect. This inhibitory effect was more obvious on the Yersinia enterocolitica.

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Background&Objective: Staphylococcus aurues is on important cause of community and hospital- aquired infections. Caused by methicillin or oxacillin- resistant s.aureus (MRSA) are mainly nosocomial and are increasingly from many countries word wide. Many attempt have been made by the reasearchers to find new compounds as a subsitute for this antibiotics. The aim of this study was to investigate the antimicrobial activity of alcoholic extracts of 20 medical plants species of Golestan provience on clinical and standard strains of MRSA and MSSA and comprative and detect the best medical plant. Materials&Methods: In this study the compunds of the plant were extracted by percolation method and the effect of ethanolic extract of 20 Iranian medical plants against methicillin resistant and methicillin sensitve strains were assessed by disc diffusion method and each test were repeated 3 times and mean inhibition zone were recorded and then, the minimum inhibitory concentration (MIC) of the extracts, that show good inhibition zone in disc diffusion method, was determined by the micro broth dilution method. Results: The results of antibacterial activity of the ethanolic extracts of 20 plants revealed that, the ethamlic extracts of 8 plants have the best effect on strains and the maximum mean inhibition zone was 22.4 mm and the lowest MIC of plants was 0.01 mg/ml. Conclusion: The result of this study indicate that, ethanolic extract of Eucalyptus. Global, Peganum.hermla, Punica.granatum, Berberis.vulgaris, Ttamarixaphylla, Nnigella.sativa, Hypericum.perforatum AND, Artemisia. Herbaalba have the best antibacterial effect against MRSA andMSSA. The result obtained from these plants might be considered sufficent for further study.