Effect of Nanoencapsulation on the Antimicrobial and Antibiofilm Activities of Algerian Origanum glandulosum Desf. against Multidrug-Resistant Clinical Isolates

The emergence of multidrug-resistant (MDR) bacteria is a danger to public health and exposes patients to high risk, increasing morbidity and mortality worldwide. For this purpose, three months of evaluation of MDR's prevalence and antimicrobial susceptibility patterns in the military regional university hospital of Constantine from different services and samples was carried out. Among a total of 196 isolates, 35.2% were MDR. The use of essential oils such as Origanum glandulosum Desf. as an alternative to antibiotics is attractive due to their rich content of bioactive compounds conferring many biological activities. Also, to overcome the drawbacks of using oils as the hydrophobicity and negative interaction with the environmental conditions, in addition to increasing their activity, encapsulation for the oil was performed using high-speed homogenization (HSH) into nanocapsules and high-pressure homogenization (HPH) into nanoemulsion. Nine volatile constituents were determined using gas chromatography-mass spectrometry analysis (GC-MS) in hydrodistilled oil with thymol, carvacrol, p-cymene, and gamma-terpinene as dominants. A dramatic decrease in the major volatile components was observed due to the use of HSH and HPH but generated the same oil profile. The mean particle size of the nanoemulsion was 54.24 nm, while that of nanocapsules was 120.60 nm. The antibacterial activity of the oil and its nanoparticles was estimated on MDR isolates using the disk diffusion, aromatogram, and broth microdilution methods. Consistent with the differences in volatile constituents, the oil exhibited a higher antibacterial activity compared to its nanoforms with the diameters of the inhibition zone against E. coli (20 mm), S. aureus (35 mm), and A. baumannii (40 mm). Both formulations have shown relatively significant activity against the biofilm state at sub-inhibitory concentrations, where nanoemulsion was more potent than nanocapsules. The results obtained suggested that nanoformulations of essential oils are strongly recommended for therapeutic application as alternatives to antibiotics.