In vitro antibacterial activity of extracts of Dalbergia sissoo and Aegle marmelos against Enterotoxigenic Escherichia coli from calves

Neonatal calf diarrhoea (NCD) is the most common cause of morbidity and mortality in pre-weaned dairy calves, causing huge economic and productivity losses to dairy industry worldwide. Enterotoxigenic E. coli (ETEC) is one of the important causes of neonatal diarrhoea and high mortality in very young calves. Shisham (Dalbergia sissoo) leaves and Bael (Aegle marmelous) unripe fruit have been used in diarrhoea and dysentery with very good results. Hence the present study was conducted to evaluate the in vitro antibacterial activity of the aqueous and methanolic extract of Dalbergia sissoo and Aegle marmelos against 16 E. coli isolated from colibacillosis affected diarrhoeic calves in Bikaner district of Rajasthan. The average zones of inhibitions of aqueous extract of Aegle marmelos and methanolic extract of Dalbergia sissoo against E. coli were 23.75±0.34 mm, 18.75±0.32 mm, 16.5±0.24 mm, 11.58 ±0.14 mm and 7.88±0.24 mm at concentrations of 1000 mg/ml, 500 mg/ml, 250 mg/ml 125 mg/ml and 62.5 mg/ml, respectively. The average zones of inhibition of aqueous extract of Dalbergia sissoo and methanolic extract of Aegle marmelos against E. coli were 24.75±0.20 mm, 19.87±0.34 mm, 17.25±0.24mm, 12.86±0.13 mm and 8.50±0.14 mm at concentrations of 1000 mg/ml, 500 mg/ml, 250 mg/ml 125 mg/ml and 62.5 mg/ml, respectively. The maximum zone of inhibition was reported by aqueous extract of Dalbergia sissoo and methanolic extract of Aegle marmelos (>24 mm of diameter) at concentration of 1000 mg/ml. Based on average zone of inhibition, the in vitro antibacterial activity of aqueous extract of Dalbergia sissoo and methanolic extract of Aegle marmelos was found to be more against E. coli as compared to aqueous extract of Aegle marmelos and methanolic extract of Dalbergia sissoo at varying concentrations. In conclusion, both combination of aqueous and methanolic extract of Dalbergia sissoo and Aegle marmelos showed in vitro antibacterial properties against E. coli