Fatty acids from Hermetia illucens larvae disrupt membrane integrity in colistin-resistant Acinetobacter baumannii

BACKGROUND: The overuse and prolonged application of antibiotics have led to the emergence of multidrug-resistant bacterial pathogens, notably Acinetobacter baumannii, a leading cause of nosocomial infections and increased mortality in healthcare settings. In natural conditions, fatty acids possess well-documented antibacterial activity. This research investigates an eco-friendly way to extract fat from Hermetia illucens (HI) larvae to analyze its antimicrobial properties against colistin-resistant A. baumannii ATCC 19606. METHODS: Larval fat from H. illucens was processed using a sustainable extraction protocol to yield multiple fractions. Antibacterial activity was assessed via disc diffusion and broth microdilution assays. The most potent fraction, acidic water methanol extract 3 (AWME3), was further evaluated for inhibition zone diameter, minimum inhibitory concentration (MIC), MIC50, and minimum bactericidal concentration (MBC). Salt tolerance assays were conducted under 0-10% NaCl conditions to assess robustness. Morphological and intracellular changes were examined using electron microscopy. RESULTS: Among the obtained fractions, the third acidic water methanol extract (AWME3) demonstrated the highest activity against A. baumannii ATCC 19606. AWME3 exhibited a clear inhibition zone of 18.1 ± 0.35 mm at 20 mg/mL. The minimum inhibitory concentration (MIC), MIC50, and minimum bactericidal concentration (MBC) were found to be 380 µg/mL, 222 µg/mL, and 380 µg/mL, respectively. Complete inhibition of colony formation was observed at both MIC and 2×MIC levels under NaCl concentrations ranging from 0 to 10%. Electron microscopy revealed that fatty acids severely damaged bacterial cell walls and membranes, increasing permeability and causing leakage of cell contents, leading to cell death. CONCLUSIONS: Fatty acid-enriched extracts from H. illucens larvae, particularly AWME3, exhibited potent antibacterial activity against colistin-resistant A. baumannii, likely through membrane-disruptive mechanisms. These findings highlight the potential of insect-derived bioactive compounds as sustainable alternatives for managing MDR pathogens.