The in vitro antibacterial activity of Morinda lucida and Acalypha wilkesiana leaf extracts against Campylobacter and Escherichia coli relevant in poultry infections

Abstract

The most common cause of bacterial diarrhea in humans worldwide is infection with Campylobacter species, particularly Campylobacter jejuni and C. coli. The disease is zoonotic and domestic animals such as poultry, pigs and cattle may act as reservoirs. Colibacillosis is caused by Escherichia coli which is both a food and water borne zoonotic disease from poultry, calves and pigs. The development of resistant strains against the conventional antibiotics has reduced the efficacy of the antibiotics. Therefore, there is urgency to develop drug leads or templates with good activity against these pathogens. The antibacterial activity and safety of acetone, methanol, hot and cold aqueous leaf extracts of Morinda lucida and Acalypha wilkesiana on Campylobacter coli and selected clinical isolates of Escherichia coli was investigated in vitro using serial microdilution and cytotoxicity assays. The MIC values of selected plant extracts against the test organisms generally ranged from 0.03 to 2.50 mg/ml. MIC values of the acetone extracts ranged from 0.03 to 0.46 mg/ml, methanolic extract MICs ranged from 0.15 to 0.78 mg/ml, cold aqueous extract MICs ranged from 0.03 to 2.50 mg/ml while MICs of the hot aqueous extracts ranged from 0.03 to 1.25 mg/ml. The MIC of the positive control, gentamicin, against Campylobacter species ranged from 0.001 to 0.62 mg/ml while those of Escherichia isolates were extremely promising, ranging from 0.0002 to 0.001 mg/ml. The LC50 values of the acetone and cold aqueous extracts of Morinda lucida against the intestinal CaCo‐2 cell line were 0.46 and 0.58 mg/ml respectively while those of acetone, methanolic and hot aqueous extracts of Acalypha wilkesiana were 1.56, 0.11 and 0.19 mg/ml respectively. The selectivity index (SI) values of the acetone extract of Morinda lucida ranged from 2.55 to 9.20 while those of the cold aqueous extracts ranged from 0.23 to 19.33 with the acetone extract having better SI than the cold aqueous extract. The SI values of the acetone extract of Acalypha wilkesiana ranged from 2.22 to 52, methanolic extract ranged from 0.14 to 0.73 and hot aqueous extract ranged from 0.15 to 6.33 with the acetone extract having the best SI relative to cold aqueous, methanolic and hot aqueous extracts of both plant extracts, indicating that the observed antimicrobial activity was not due to toxicity to mammalian cells. These results highlight the potential of Morinda lucida and Acalypha wilkesiana as an alternative for treatment of campylobacteriosis and colibacillosis in poultry. However, in vivo data is necessary to determine the potential usefulness of these plant speciesThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.