In Vitro and In Vivo Studies of the Use of Some Medicinal Herbals against the Pathogen Aeromonas hydrophila in Goldfish

Abstract

Aeromonas hydrophila is a ubiquitous and opportunistic bacterial pathogen that produces ulcerative dermatitis under stress conditions and inflicts severe losses on global fisheries and fish culture. This study evaluates the antimicrobial potency of aqueous and ethanolic decoction (individual extract) and concoction (mixed extract) of three common medicinal herbs, turmeric Curcuma longa, Tulsi plant Ocimum sanctum, and neem Azadirachta indica, against the in vitro growth of A. hydrophila. Among the decoctions, A. indica exhibited the most potent antibacterial property (P < 0.05) against A. hydrophila. Among the concoctions, both the aqueous and ethanolic triherbal extracts mixed in the ratio of 1:1:1 had higher antibacterial activity (P < 0.05) than the other concoctions and decoctions. Goldfish Carassius auratus (10 +/- 2 g) were challenged with A. hydrophila intramuscularly in the caudal region with two separate doses (days 1 and 3) of 50 microL/fish (1.8 x 10(3) colony-forming units per milliliter). On days 9 (early) and 15 (late) of infection, fish were held in a net and dip treated for 5 min daily in a 1-L solution of 1% aqueous triherbal concoction. Red blood cell (RBC) count, hemoglobin, and hematocrit levels of the infected group were significantly higher (P < 0.05) than those of the control group. In the early treated group, all of the affected profile values returned to near normal, while the late-treated group registered a partial recovery, such as improved RBC count. The derived hematological values, such as mean corpuscular volume, mean corpuscular hemoglobin, and mean corpuscular hemoglobin concentration, of the early and late-treated groups also significantly declined (P < 0.05) but were restored to near normal (P > 0.05) only in the early treated group. The results suggest that dip treatment of A. hydrophila-infected goldfish in an aqueous triherbal concoction had a synergistic restorative effect on the hematological variables.