In vitro control of multidrug-resistant bacterial isolates and fungi by essential oils and their nanoformulations

Abstract

Antibiotic resistance is one of the biggest global public health threats. The abuse of antibiotics and the emergence of resistant strains of bacteria undermine the effectiveness of conventional treatments. Natural molecules extracted from medicinal plants offer a promising alternative to combating this resistance, with nanoformulation improving their bioavailability and therapeutic effectiveness. The objectives of this study are to provide a comprehensive analysis of antibiotic resistance within a clinical setting,explore the potential of natural EOs as alternative antimicrobial agents, and assess the efficacy of their nanoformulations in enhancing biological activity.A retrospective study conducted at the service of infection diseases at CHU Setif during the initial phase of our investigation revealed alarmingly high rates of resistance to amoxicillin (100%), cefazoline (>70%), and cefotaxime (58.06%). Escherichia coli ESBL represented the most common bacterial strain identified (29.03%). In the second part, the study examined the extraction by hydrodistillation of essential oils (EOs) from Algerian Satureja hortensis L.(ASHEO) and Cymbopogon citratus (DC.) Stapf (LGEO), and the microfluidization technique was used to get their nanoformulations.The GC-MS apparatus was utilized for a comparative examination of ASHEO and LGEO with their microfluidization nanoemulsions (MF-ASHEO and MF-LGEO) volatile content. MF-ASHO showed 8 compounds (99.56%) vs ASHEO's 26 compounds (95.46%). The identified components in MF-LGEO represented 97.53% of the total nanoemulsion oil, which was similar to the hydrodistilled LGEO (97.73%). The essential oils and nanoformulations showed antibacterial and antibiofilm properties,while ASHEO and LGEO showed superior efficacy against pathogenic isolates of Gram-positive and Gram-negative bacteria. ASHEO effectively exhibited activity against all tested bacterial strains with inhibition zones measured between 55.66 mm and 29.66 mm, and the biofilm formation of E. coli and P. aeruginosa was suppressed by over 60%, while LGEO demonstrated complete inhibition of B. subtilis. The bactericidal and bacteriostatic effects of carvacrol on the target proteins were validated by ADME and in silico analyses. Additionally, essential oils, especially MF-LGEO, showed antifungal properties against mycotoxigenic fungi including Aspergillus, Penicillium and Fusarium strains by influencing their growth rates and suggesting potential treatment for toxigenic fungal contamination. The study also found that essential oils and nanoformulations showed promising cytotoxicity against three cell line strains, with microfluidization enhancing anti-inflammatory effects, and these findings were linked to alterations in nanoformulation components. Studied essential oils revealed moderate antioxidant effects in radical scavenging, with an IC50 value of 536.47 ± 21.99 µg.mL-1 for ASHEO and an IC50 value equal to (82.87 ± 2.15 µg.mL-1). The microfluidization procedure has a profound impact on both the volatile content and biological activity of the oil.Our findings reassure the use of S.hortensis and C.citratus for their valuable essential oils and to prevent mycotoxigenic diseases and pathogenic-resistant bacteria.