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.