Luminescence light produced by luminescent vibrios can be used for toxicity assessment of various chemicals, such as nanoparticles with antimicrobial properties. Hence luminescent vibrios are recognized as an opportunistic pathogen and use of antibiotics against them may cause problems such as emerging antibiotic resistant strains. In this study, we tried to use zinc oxide nanoparticles as the new alternative. Isolation was performed on shrimp farm water samples using special medium, and luminescent bacteria were islated according to light output observation in dark. Morphological and molecular tests were examined on isolated Vibrios. Finally the strain was identified by 16S rRNAgene sequencing analysis. ZnO NPs were synthesized by solvothermal methods and different concentrations of nanoparticles (100, 50, 25 and 12. 5 microgram per mililiter) were added to the isolated bacteria using microdilution method. Then, MIC and MBC were determind by ELISA reader apparatus. To determine the minimal toxic concentration of the nanoparticles against isolated bacteria, several concentration of nanoparticles (25, 12. 5, 6. 25, 3. 125 and 1. 5 microgram per mililiter) were contacted with bacteria in the early of the stationary phase and decrease of luminescence light was evaluated with luminometer apparatus. Morphological characteristics and 16S rRNA gene analysis showed that isolated strains had 99% similarity to V. harveyi. Synthesized nanoparticles had the particle size of about 35nanometer. In addition, the results showed that MIC and MBC for ZnO nanofluid against both two isolates were100 μg/ml. Also effective concentration of ZnO NPs against bacteria that decrease luminescence light intensity more than 50%, was 3. 125 μg/ml for isolated strain (VHGA) and 6. 25 μg/ml for isolated strain (VHGB).

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