This study was conducted to examine

in vitro antibacterialpotential from seed methanol extract of Peganum harmala (L) against some fish pathogenic bacteria including Lactococcus garvieae, Aeromonas hydrophila, Yersinia ruckeri and Pseuodomonas putida isolated from diseased rainbow trout (Oncorhynchus mykiss). The antibacterial activity of extracts was evaluated using disc diffusion assay, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). MICS were measured by serial dilution and the microplate assays. Results showed that the methanol extract of P. harmala was bactericidal for all test acteria. The MICs of extract using serial dilution and microplate method were 0.6 mg mL-1 and 0.312 to 0.625 mg mL-1 against P. putida and 0.8 mg mL-1 and 0.625 to 1.25 mg mL-1 against L. garvieae, A. hydrophila, Y. ruckeri, respectively which was confirmed by MBC determination. Thus, the antibacterial activity of seed extract of P. harmala can be comparable as an alternative in the control of infectious by these Microorganisms.