In vitro and in vivo efficacy of partially purified herbal extracts against bacterial fish pathogens

Abstract

The effect of partially purified extracts of sea grass (Cymodocea serrulata), turmeric (Curcuma longa), Spirulina (Spirulina platensis), and beet root (Beta vulgaris) on the antimicrobial, antioxidant, and hemato-biochemical changes in ornamental dotty back, Pseudochromis dilectus against isolated fish bacterial pathogens (Proteus mirabilis, Bacillus pumilus, and Staphylococcus sciuri) under in vitro and in vivo conditions is reported. Among the extracts turmeric extract exhibited significant antibacterial activity. The extract possesses the highest antioxidant property and phenol content; the GC–MS analysis revealed the highest presence of Ar-turmerone (42.85%) and Curlone (18.80%). The potential fractions possess reducing power and free radical scavenging activity. The mortality against P. mirabilis at doses of 2.5×108 and 2.5×108CFU was 100% whereas against S. sciuri (2.5×107 and 2.5×108) it was 70 and 80%. The highest bacterial load was observed in kidney (3.1×107CFU/g) and liver (2.6×108CFU/g) against P. mirabilis. The LD50 study suggested that all the fish die at doses of 2.5×107 (CFU/fish) and 2.5×108 (CFU/fish) after 15days of challenge with P. mirabilis. Among the purified sub fractions, the sub-fraction II (F-II) at 5 and 10mg/ml resulted in elevated levels of WBC and RBC, lymphocytes, and neutrophils; further the percentage of monocytes and granulocytes, total protein, total lipid, and glucose also increased significantly. At 1mg/ml the relative percent survival (RPS) was 100% in sub-fraction II (F-I) group as in control. With 5mg/ml in F-I and 1mg/ml in F-II group the RPS was 94%; however, in 10mg/ml of F-I and 5mg/ml of F-II groups the RPS declined to 89%. The lowest mortality of RPS (79%) was observed in 10mg/ml in F-II group. The present results suggest that the partially purified turmeric extract elevated antimicrobial and antioxidant activities by improving the hemato-biochemical profiles and survival rate in P. dilectus against P. mirabilis. Statement of relevanceThe success of any fish culture depends on the health status of cultivated species. Fish diseases are one of major threats in aquaculture industry inflicting heavy mortality in the world. To prevent and control of the diseases traditionally was used several antibiotics or chemicals during the last few decades. However, these methods have been criticized for their negative impacts such as accumulation of drugs in tissues, development of drug resistance, and immunosuppression. Several herbal and their active principles possess better antioxidant activity, phenols content, reducing power, and free radical scavenging activity. Therefore in the present study was isolated new fish pathogen from the infected fish and to investigated antioxidant activity and their pathogenicity and hematological changes in dotty back, P. dilectus against P. mirabilis. This work is novel in aquaculture to design or prepare cost effective drug or feed for fishes.