The inhibitory effect of silver nanoparticles on the bacterial fish pathogens Streptococcus iniae Lactococcus garvieae Yersinia ruckeri and Aeromonas hydrophila

The aim of this study was to assess the antibacterial effects of silver nanoparticles(nanocid®) on 30 isolates of gram-positive and gram-negative bacteria that are pathogenic tofish, which consisted of strains of , ,and we used the liquid dilution method to find the minimumbactericidal concentration (mbc) using sub-culturing on the blood agar 30, 60 and 90 minutesafter the inoculation of these bacteria. isolates were prepared in sterile phosphate bufferedserial dilutions of silver nanoparticles. for (14 isolates) the results showed that thembcs were in a range of 5 to 0.15 μg/ml 30-90 minutes post-inoculation. for (14isolates) the results showed that the mbcs were in a range from more than 10 μg/ml to 0.62μg/ml 30-90 minutes post-inoculation. also, the range of mbcs for was 0.31μg/ml to less than 0.15 μg/ml, while the range of mbcs for was from 2.5 to 0.62μg/ml 30 to 90 minutes post-inoculation, respectively.generally, the bacterial growth for thesebacterial species was reduced from 1 × 10 cells/ml to no growth compared to initial inoculumsof 10 cells/ml during 90 minutes after exposure to silver nanoparticles. no remarkable changewas found in the bacterial count for the control samples (pbs without silver nanoparticles)during the experiment.