Development of nanoemulsions for the delivery of hydrophobic and hydrophilic compounds against carbapenem-resistant Klebsiella pneumoniae

Antimicrobial resistance (AR), particularly the limited antimicrobial activities of antibiotics and natural compounds, has prompted research into new antimicrobials. Nanoemulsions (NEs) have been found to improve the activity of antimicrobial compounds. This study developed clove essential oil-in-water NEs (CEO-NEs) and water-in-oil-in-water NEs co-encapsulating CEO and meropenem (CEO–MEM-NEs) to investigate the antibacterial activity of these loaded NEs against carbapenem-resistant Klebsiella pneumoniae. Ultrasonication was used to prepare CEO-NEs and CEO–MEM-NEs. Tween 80 and Imwitor 375 surfactants were used to produce CEO-NEs while Tween 80, Imwitor 375, and PGPR were used to produce CEO–MEM-NEs. Droplets' sizes were 138 ± 1.769 and 183.600 ± 0.889 for CEO-NEs and CEO–MEM-NEs, respectively. The resultant NEs were monodispersed, negatively charged, and physically stable. The antibacterial activities of NEs were investigated using broth microdilution, checkerboard, and time-kill assays to determine the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). CEO-NEs (0.16% CEO MIC) and CEO–MEM-NEs (0.08% CEO and 1 μg mL(−1) MEM MICs) completely inactivated K. pneumoniae, and showed functional stability after two weeks of storage at 4 °C. In conclusion, the formulated NEs significantly enhanced the antibacterial activity of CEO and MEM and have great potential as delivery systems of antimicrobial compounds.