Extract of Pterocarpus santalinoides (L’Her. Ex Dc) Leaf Decolonizes Escherichia coli on and in the Larvae of Housefly Intended for Feed Meal

Maggot meal is a sustainable alternative to fish meal in organic poultry production. However, maggots are often raised in environments contaminated with pathogenic bacteria, posing safety concerns. This study evaluated the efficacy of Pterocarpus santalinoides ethanol leaf extract in reducing Escherichia coli colonization on housefly maggots. The in vitro antibacterial activity of the extract was assessed using the broth dilution method, determining the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against E. coli. The larvicidal concentration and acute toxicity (LD50 = 60.334 mg/mL) of the extract on housefly larvae were also evaluated. The extract demonstrated significant antimicrobial activity with a MIC of 25 mg/mL and MBC of 50 mg/mL. When applied to E. coli-inoculated maggots, the extract eradicated the bacterium at 50 mg/mL, both on the surface and internally, within 20 hours. A concentration-dependent antibacterial effect was observed, with complete elimination of E. coli. This study highlights the potential of P. santalinoides extract for ensuring the microbiological safety of maggot meal used in animal feed. Further research is needed to optimize dosage and evaluate the extract's safety in farm animals.