Modulatory-antibiotic activity of the essential oil from Eucalyptus citriodora against MDR bacterial strains.

The growing number of bacterial strains resistant to therapeutic agents has been surpassing the various antibiotics developed by the chemical and pharmaceutical industries. This problem has driven the development of research using agents with antimicrobial potential, with an emphasis on plant-derived natural products. This study evaluated the chemical compounds present in Eucalyptus citriodora essential oil (EOEc) cultivated in northeastern Brazil and its properties as an antibacterial agent and resistance modifier against methicillin-resistant Staphylococcus aureus (MRSA) and ß-lactamase-producing strains. The EOEc was obtained using the hydrodistillation method, later analyzed by GC/MS, presenting a total of twelve compounds, with citronellal (65.45%); citronellol (14.87%); isopulegol (11.80%) and citronellyl acetate (2.51%) as its main constituents. The microdilution test was used to determine the minimum inhibitory concentration (MIC) and the bacterial resistance modulation of the essential oil. The EOEc did not present significant activity against the tested strains (MIC > 1000 µg mL-1). However, when evaluating the capacity of the EOEc to modify the resistance of S. aureus and E. coli strains to different antimicrobials, synergistic effects were obtained with reduced MIC values for all tested antibiotics being obtained. The EOEc showed antimicrobial and ß-lactam optimizing potential against resistant strains, presenting itself as a possible alternative for the use of these drugs at concentrations lower than those indicated against resistant strains.

Study bioprospecting of medicinal plant extracts of the semiarid northeast: contribution to the control of oral microorganisms.

Dental pathologies can be caused by plaque-forming bacteria and yeast, which reside in the oral cavity. The bacteria growing in dental plaque, a naturally occurring biofilm, display increased resistance to antimicrobial agents. The objective was the evaluation of a preclinical assay of medicinal plants of the semiarid region from the northeast against oral pathogenic microorganism, aiming at bioprospecting a new product. The selection of plant material for this study was based on the ethnobotanical data on the traditional use of plants from the semiarid region. The thirty extracts were subjected to the determination of antibiofilm activity against gram-positive, gram-negative bacteria and yeast. The hydroalcoholic extract which showed positive antibiofilm activity against most of the microorganisms tested in agar diffusion assay was further tested for the determination of minimum inhibitory concentration (MIC) and Bioassay with Artemia salina. Plant samples tested in this study exhibited good antibiofilm activity for the treatment of oral problems. The Schinopsis brasiliensis showed greater activity for Pseudomonas aeruginosa and Staphylococcus aureus, but toxicity against Artemia salina.

Phytochemical characterization and mutagenicity, cytotoxicity, antimicrobial and modulatory activities of Poincianella pyramidalis (Tul.) L.P. Queiroz.

In this study, the chemical composition, genotoxic, cytotoxic and antibacterial-modulating activities of the P. pyramidalis (NPpE) extract was evaluated. The fingerprint chromatogram was determined using HPLC-DAD. The NPpE Minimal Inhibitory Concentration (MIC), as well as that of antimicrobial drugs in the presence and absence of the extract, were evaluated using the microdilution method against Gram positive bacteria. In vivo assays with mice were used for the determination of the extract's genotoxicity and cytotoxicity. The presence of the polyphenol catechin was confirmed in the extract. The extract showed significant antimicrobial activity (MIC ≤ 1000 µg mL-1) against Staphylococcus aureus, Streptococcus oralis and S. mutans. When the NPpE was associated with several antimicrobials, the MIC of most of these were significantly reduced (P < 0.001) demonstrating good prospective usage in antimicrobial therapy. The extract has mutagenic and cytotoxic potential, however, further studies should be performed to confirm their toxicity.

Evaluation of the Interaction between the Poincianella pyramidalis (Tul.) LP Queiroz Extract and Antimicrobials Using Biological and Analytical Models.

Poincianella pyramidalis (Tul.) LP Queiroz (Fabaceae) is an endemic tree of northeastern Brazil, occurring mainly in the Caatinga. Its medicinal use is widespread and is an important therapeutic option against diarrhea, dysentery, and respiratory and urinary infections, among other diseases. In this study we determined the chemical marker and evaluated the interaction between P. pyramidalis extract and a commercial antimicrobial through the use of biological and analytical models. To obtain the extract, an ethanol-water mixture (50:50 v/v) was used as solvent. It was nebulized in a spray dryer using colloidal silicon dioxide as a drying adjuvant. The extract (ENPp) was subjected to HPLC analysis to verify the presence of certain secondary metabolites. The Minimum Inhibitory Concentration (MIC) of the extract against Gram-negative bacteria was determined by broth microdilution and the MIC of synthetic antimicrobial drugs in the presence and absence of the extract. The antioxidant activity of ENPp was evaluated by the DPPH method. The compatibility between the antimicrobial and the extract was evaluated by thermal analysis (TG/DTA). The acute toxicity of the extract was evaluated in vivo in rodents. The results indicate significant additive action of the extract on synthetic antibiotics, considerable antioxidant activity and absence of toxicity. This extract shows high potential for the development of formulations for antimicrobial therapy when used with a vegetable-active ingredient.

Antibiotic resistance modulation by natural products obtained from Nasutitermes corniger (Motschulsky, 1855) and its nest.

Insects and their products are included in the traditional pharmacopoeia of various ethnic groups worldwide. In the Brazilian semiarid region can be highlighted the use of the termite Nasutitermes corniger for the treatment of various diseases. This study evaluated the ethanol extract of N. corniger and its nest as an antimicrobial agent and as a modulator of bacterial resistance against multidrug strains. The Minimum Inhibitory Concentration (MIC) of the extract on Staphylococcus aureus and Escherichia coli by microdilution was determined, as well as MIC of antibiotics in the presence and absence of extract. Despite having no significant antimicrobial activity (MIC â©¾ 1000 µg mL(-1)), the extract showed additive activity to the antibiotic efficacy, significantly reducing its MIC. These results suggest that N. corniger and its nest are promising natural products for use in antimicrobial therapy.

Modulation of the erythromycin resistance in Staphylococcus aureus by ethanolic extracts of Ximenia americana L and Schinopsis brasiliensis Engl / Modulación de la resistencia a la eritromicina en Staphylococcus aureus por extractos etanólicos de Ximeniaamericana L y Schinopsis brasiliensis Engl

It was evaluated the in vitro efficacy of ethanolic extract of leaves and bark of Ximenia americana L and Schinopsis brasiliensis Engl. alone and in association with erythromycin as modulators of microbial resistance against six clinical isolates of Staphylococcus aureus resistant to erythromycin (SA1-SA6) and S. aureus ATCC 25923 by the microdilution method. The extracts were also subjected to bioassay with Artemia salina. The ethanolic extract of barks of X. americana showed a synergistic effect with erythromycin against SA01, SA03 and SA04. The leaf extract of S. brasiliensis exerted synergistic effect against SA03 and the bark extract showed against SA01 and S03. The results suggest that extracts from S.brasiliensis and X. americana have potential as modulator agents of bacterial resistance, which could be used as adjuvants in the treatment of infections by S. aureus resistant to erythromycin, with previous studies of toxicity.

Se evaluó la eficacia in vitro de los extractos etanólicos de hojas y corteza de Ximenia americana L y Schinopsis brasiliensis Engl solos y en asociación con eritromicina como moduladores de la resistencia microbiana frente a seis aislados clínicos de Staphylococcus aureus resistentes a Eritromicina (SA1-SA6) y S. aureus ATCC 25923, por el método de microdilución. Además se determinó la actividad tóxica de los extractos contra Artemia salina. Solo el extracto etanólico de la corteza de X. americana mostró un efecto sinérgico con la eritromicina frente a SA01, SA03 y SA04. El extracto de las hojas de S. brasiliensis ejerció efecto sinérgico contra SA03 y el extracto de corteza, contra SA01 y S03. Los resultados sugieren que S. brasiliensis y X. americana tienen potencial como agentes moduladores de la resistencia bacteriana, que podrían ser utilizados como adyuvantes en el tratamiento de infecciones por S. aureus resistentes a eritromicina, con estudios previos de toxicidad.