Effects of Eucalyptus camaldulensis, Mentha pulegium, Aloe vera Essences and Chloramine T on Growth Behavior of Streptococcus iniae and Lactococcus garvieae the Causes of streptococcosis/ lactococcosis in Farmed Rainbow Trout (Onchorhynchus mykiss)

Document Type : Research Paper


Department of aquatic animal health, Faculty of veterinary medicine, University of Tehran, Tehran, Iran


The present study aimes to evaluate the effects of Eucalyptus camaldulensis, Mentha pulegium,
Aloe vera (20, 40, 80, 160 and 320 μl/ml) and chloramine T (0.05, 0.12, 0.25, 0.5, 1 and 2mg/
ml) on the bacterial growth of Streptococcus iniae (8 isolates) and Lactococcus garvieae (12
isolates) after 30, 60 and 90 minutes and 1, 2, 4 and 10 hours post incubation at 25°C. The
liquid dilution method was used to assess the minimum inhibitory concentration (MIC) using
sub-culturing on the blood agar, after 30, 60 and 90 minutes incubation at 25°C. An increase in
the concentration of Eucalyptus camaldulensis and Mentha pulegium caused that the bacterial
growth decreased so that under the 160 and 320 μl/ml MIC of these essences after 60 and 90
minutes post incubation the growth was completely stopped. No effect was found for Aloe
vera. Chloramine T proved to be the most effective substances to these bacterial strains giving
a MIC of 0.5 and 2 mg/ml after 4 and 10 hours post incubation. The results also indicated that
all strains of S. iniae and L. garvieae isolated from farmed rainbow trout are resistant to A.
veraessence. However, E. camaldulensis, M. pulegium essences and chloramine T could be
used as potential substances for reduction of bacterial loading in the water column in farmed
rainbow trout.