Multidrug-resistant (MDR) Gram-negative bacteria remain a global public health issue due to the barrier imposed by their outer membrane and their propensity to form biofilms. It is becoming imperative to develop new antibacterial strategies. In this context, this study aims to evaluate the antibacterial efficacy of Origanum vulgare essential oil (OEO), alone and in combination with antibiotics, as well as its antibiofilm action against multidrug-resistant Gram-negative strains. OEO components were identified by gas chromatography-mass spectrometry (GC-MS), and antibacterial activity was assessed using the agar diffusion test and the microdilution method. Interactions between OEO and antibiotics were examined using the checkerboard method, while antibiofilm activity was analyzed using the crystal violet assay. Chemical analysis revealed that carvacrol was the major compound in OEO (61.51%). This essential oil demonstrated activity against all the tested strains, with inhibition zone diameters (IZDs) reaching 32.3 ± 1.5 mm. The combination of OEO with different antibiotics produced synergistic and additive effects, leading to a reduction of up to 98.44% in minimum inhibitory concentrations (MICs). In addition, this essential oil demonstrated an ability to inhibit and even eradicate biofilm formation. These results suggest that OEO could be exploited in the development of new molecules, combining its metabolites with antibiotics.

Carthamus caeruleus L. is traditionally used in Algerian medicine, particularly for burn treatment, but its therapeutic potential remains insufficiently studied. This study aimed to evaluate the antioxidant and anti-inflammatory properties of the root aqueous extract, and to perform phytochemical characterization to identify its bioactive compounds. Phytochemical analysis was conducted using spectrophotometry and reverse-phase high-performance liquid chromatography (RP-HPLC). The antioxidant potential was assessed through various assays, including ferric reducing antioxidant power (FRAP), total antioxidant capacity (TAC), DPPH radical scavenging, hydroxyl radical scavenging, ferrous ion chelation, and hydrogen peroxide decomposition. Anti-inflammatory activity was evaluated using membrane stabilization, protein denaturation, and membrane peroxidation assays. The extract exhibited moderate levels of polyphenols, flavonoids, and condensed tannins, quantified as 21.19 ± 0.37 mg GAE/g, 0.72 ± 0.013 mg QE/g, and 27.28 ± 1.04 mg TAE/g of dry extract, respectively. RP-HPLC analysis identified 22 phytochemical compounds, primarily phenolic acids, flavonoids, and tannins, with orientin and vanillin as the major constituents. The extract demonstrated significant antioxidant activity, with moderate efficacy in TAC and FRAP assays (IC₅₀ values of 5405.1 ± 4.42 and 1132.35 ± 4.97 µg/mL, respectively). Notable activities included DPPH and hydroxyl radical scavenging (34.43 ± 4.83 and 512.81 ± 9.46 µg/mL, respectively), ferrous ion chelation (2462.76 ± 1.38 µg/mL), lipid peroxidation inhibition (22.32 ± 3.31%), and hydrogen peroxide decomposition (263.93 ± 7.87 µg/mL). Additionally, the extract stabilized erythrocyte membranes under osmotic, thermal, and oxidative stress conditions (98.13 ± 0.15%, 70 ± 1.27%, and 89 ± 0.87%, respectively), inhibited ovalbumin denaturation (81.05 ± 2.2%), and protected against lipid peroxidation in brain homogenates (69.25 ± 0.89%). These findings support the traditional therapeutic applications of C. caeruleus and highlight its potential as a source of antioxidant and anti-inflammatory agents.

Avian colibacillosis remains a major threat to poultry production and food security, whereas its antibiotic-based control accelerates antimicrobial resistance. This study investigated the antibacterial potential of the hydroethanolic extract of Thymus vulgaris, alone and in combination with antibiotics, against avian pathogenic Escherichia coli (APEC). The phytochemical composition of the extract was analyzed by HPLC, while its antibacterial activity was assessed using agar diffusion and minimum inhibitory concentration (MIC) assays. Antibiotic-extract interactions were evaluated by the checkerboard method, and mechanisms of action were explored through assays targeting membrane permeability, proton pump inhibition, catalase inhibition, oxidative stress, and biofilm formation. Its antioxidant, anti-inflammatory, and cytotoxic activities were also evaluated. HPLC analysis revealed 16 phenolic compounds, including rosmarinic, ferulic, and salicylic acids, as well as flavonoids such as quercetin and luteolin, with an extraction yield of 15% ± 0.55. The extract displayed significant antibacterial activity (MIC: 5.46-10.93 mg/ml, p < 0.05). In synergy tests, the extract enhanced ampicillin efficacy 4-8-fold and showed additive effects with ciprofloxacin and tetracycline (2-4-fold). Mechanistic assays demonstrated disruption of bacterial membranes (32.66% electrolyte leakage, p < 0.05), inhibition of H⁺-ATPase proton pumps (p < 0.05), catalase activity reduction by 79.2% (p < 0.05), >50% decrease in cell hydrophobicity, and inhibition of biofilm formation (49.07-72.47%), alongside eradication of mature biofilms (41.89-64.67%) (p < 0.05). Beyond antimicrobial effects, the extract exhibited notable antioxidant capacity. In DPPH radical scavenging, the extract showed an IC₅₀ of 9.76 ± 0.228 μg/ml (p < 0.05), while in the TAC assay, it reached 467.25 ± 1.889 μg/ml (p < 0.05), and it reduced ampicillin-induced lipid peroxidation by 42.85% (p < 0.05). Anti-inflammatory testing revealed inhibition of protein denaturation (4.95-52.48% at 15-2000 µg/ml, p < 0.05), although weaker than aspirin. Hemolysis assays confirmed the extract was non-hemolytic at concentrations up to 11 mg/ml (p < 0.05). In conclusion, Thymus vulgaris extract demonstrated safe, multi-target bioactivity, supporting its potential as a promising alternative to combat avian colibacillosis and antimicrobial resistance.

Avian pathogenic Escherichia coli (APEC) represents a major challenge for the poultry industry, causing significant economic losses. This problem is exacerbated by the misuse use of antibiotics in Veterinary Medicine, leading to the emergence of resistant strains and thus creating a significant risk to Public Health. This study, carried out on 38 poultry farms in Algeria, involved the collection of 200 samples for the isolation of E. coli strains. The resistance of these strains to frequently used antibiotics was assessed using the agar diffusion method. Multiple Correspondence Analysis (MCA) was used to determine potential risk factors. The obtained results revealed that E. coli was present in 30% of samples. Alarming levels of resistance were observed against Tetracycline (81.6%), Ampicillin (78.3%), Ciprofloxacin (68.3%) and Nalidixic acid (60%). Stressful environmental conditions in poultry houses, such as temperature variations, high humidity, poor ventilation and stocking density were identified as key factors in the development of avian colibacillosis. In conclusion, the current study highlights the urgent need to strictly monitor and regulate the use of antibiotics in Veterinary Medicine and improve animal welfare in order to minimize the risk it pose to Public Health originated in the farms. In addition, it is essential that farmers maintain optimal environmental conditions in chicken rearing.