Mónica Espadero

One of the greatest threats to global public health is antimicrobial resistance (AMR), due to the increasing number of infections caused by extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae. Escherichia coli and Klebsiella pneumoniae ESBL-producing bacteria possess resistance mechanisms that inactivate β-lactam antibiotics by hydrolyzing their β-lactam ring, thereby limiting conventional therapeutic options. In response to this problem, the objective of this exploratory in vitro study was to evaluate the antimicrobial activity of Origanum vulgare (oregano) essential oil and its interaction with the antibiotic cefepime using in vitro methods. Antimicrobial susceptibility tests were performed, including determination of the minimum inhibitory concentration by the microdilution method with statistical analysis, and evaluation of the fractional inhibitory concentration index using the checkerboard method. In addition, advanced methods such as MALDI-TOF mass spectrometry for bacterial identification and PCR were employed for the identification of resistance genes. The studied strains exhibited both phenotypic and genotypic resistance. The MIC of the essential oil was 1024 µg/mL for ESBL-producing E. coli and 2048 µg/mL for ESBL-producing K. pneumoniae, whereas the ATCC strains showed higher susceptibility. The FICI values indicated synergism in E. coli (FICI = 0.188) and an additive effect in K. pneumoniae (FICI = 0.563). Oregano essential oil exhibits antimicrobial activity and the ability to potentiate the effect of cefepime, suggesting its potential as a therapeutic adjuvant. Additional studies are required, including a larger number of strains, cytotoxicity analyses, and clinical validation.

Background/Objectives: One of the greatest threats to global public health is antimicrobial resistance (AMR), due to the increasing number of infections caused by extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae. Escherichia coli and Klebsiella pneumoniae ESBL-producing bacteria possess resistance mechanisms that inactivate β-lactam antibiotics by hydrolyzing their β-lactam ring, thereby limiting conventional therapeutic options. In response to this problem, the objective in this exploratory in vitro study was to evaluate the antimicrobial activity of Origanum vulgare (oregano) essential oil and its interaction with the antibiotic cefepime using in vitro methods. Methods: Antimicrobial susceptibility tests were performed, including determination of the minimum inhibitory concentration by the microdilution method with statistical analysis, and evaluation of the fractional inhibitory concentration index using the checkerboard method. In addition, advanced methods such as bacterial identification by MALDI-TOF mass spectrometry and PCR were employed for the identification of resistance genes. Results: The studied strains exhibited both phenotypic and genotypic resistance. The MIC of the essential oil was 1024 µg/mL for ESBL-producing E. coli and 2048 µg/mL for ESBL-producing K. pneumoniae, whereas the ATCC strains showed higher susceptibility. The FICI values indicated synergism in E. coli (FICI = 0.188) and an additive effect in K. pneumoniae (FICI = 0.563). Conclusions: Oregano essential oil exhibits antimicrobial activity and the ability to potentiate the effect of cefepime, suggesting its potential as a therapeutic adjuvant. Additional studies are required, including a larger number of strains, cytotoxicity analyses, and clinical validation.

Throughout history, plants have been indispensable in the development of society due to their high content of bioactive substances, which are used in different industries such as food, pharmaceutical, and cosmetics. Curcuma longa is a perennial species that belongs to the Zingiberaceae family, which is used for therapeutic purposes due to its anti-oxidant, anti-inflammatory and antibacterial properties, among others. This research evaluates the antibacterial activity of ethanolic and acetonic extracts of Curcuma longa against Propionibacterium acnes, recently renamed Cutibacterium acnes, that has long been implicated in the pathogenesis of acne. Secondary metabolites were identified by phytochemical screening tests. Curcuminoids determination was carried out by using TLC (thin-layer chromatography) and the phenolic compounds were quantified by the Folin-Ciocalteu assay. The antibacterial activity was evaluated using the Kirby-Bauer method with different treatments (50,75 and 100%) and broth microdilution method was used to determine the minimum inhibitory concentration (MIC). The extracts showed the presence of phenolic compounds, flavonoids, terpenoids, and tannins, confirming the presence of curcuminoids. In the quantification of phenolic compounds, no significant differences in their composition were observed. The treatment 100% of acetonic extract of Curcuma longa exhibited an inhibition percentage of 48.79% compared to the ethanolic ex tract 75% treatment, which reached 31.67%. Additionally, the acetonic extract showed a minimum inhibitory concentration of 15.62 µg/mL, while for the ethanolic extract, it was 31.25 µg/mL. These findings highlight the potential antibacterial activity of the acetonic extract against Cutibacterium acnes, which could make it a promising natural option for acne control.

The use of plants has been increasing by the presence of bioactives, which is an opportunity in the creation of products such as medicines, food and cosmetics. Taraxacum officinale (Dandelion) and Melissa officinalis (Toronjil), are cosmopolitan species with great therapeutic potential, traditionally used for their anti-inflammatory, antioxidant and antimicrobial activity. Therefore, this research evaluates the antimicrobial activity of the methanol extracts of Taraxacum officinale and Melissa officinalis on Staphylococcus aureus using in vitro tests. Analyzes of secondary metabolites were performed by phytochemical screening tests, as well as the identification of possible compounds responsible for antimicrobial activity using the Bioautography technique. The phenolic compounds were quantified by the Folin-Ciocalteu assay, and the antimicrobial capacity of the extracts was evaluated by the Kirby-Bauer method. Phytochemical screening revealed the presence of alkaloids, flavonoids, saponins, phenols and tannins in both extracts. Using Bioautography, potentially inhibitory metabolites were identified, including chlorogenic acid (Rf 0.45), taraxasterol (Rf 0.65), caffeic acid (Rf 0.87), geraniol (Rf 0.2), citral (0.42) and citronellal (0.8). In addition, a greater number of phenolic compounds (112.20 ± 10.13 mg EAG/g MS) was observed in the extract of Melissa officinalis, while the extract of Taraxacum officinale showed a greater bacterial inhibition capacity, reaching 65.49%.

Euphorbia aff. Viridis (Klotzsch & Garcke) boiss, es una especie vegetal perteneciente a la familia Euphorbiaceae, forma parte de las más diversas del continente americano, y es empleada en múltiples tratamientos en medicina ancestral en los Andes Ecuatorianos. En el presente estudio se analizaron los compuestos orgánicos extraídos de las hojas de la planta. Se estableció la descripción y clasificación taxonómica de la especie vegetal. Para el estudio fitoquímico se analizó fenoles, taninos, saponinas, cumarinas, lactonas y flavonoides, observándose resultados positivos para cada compuesto químico. La caracterización química mediante Cromatografía de Gases acoplada a espectrometría de Masas GC-MS, mostró 36,66% de lanosterol, 12,25% β-sitosterol, 5,11% 3-β-colest-4-en-3-ol, 4,73% Ácido hexadecanoico como elementos mayoritarios. El ensayo microbiológico de extractos etanólicos mostró un porcentaje de inhibición del 44% sobre Klebsiella pneumoniae (ATCC70693) y 43% en Escherichia coli (ATCC10536) con una CMI de 30µl/ml para cada cepa, y se observó un resultado negativo de inhibición para Staphylcoccus aureus (ATCC24213). Los extractos orgánicos de Euphorbia aff. Viridis (Klotzsch & Garcke) Boiss, presentaron actividad antimicrobiana pudiéndose observar su potencial uso como agentes antimicrobianos.