Synergistic antibiofilm efficacy of a gallotannin 1,2,6-tri-O-galloyl-β-D-glucopyranose from Terminalia chebula fruit in combination with gentamicin and trimethoprim against multidrug resistant uropathogenic Escherichia coli biofilms.

In recent years the emergence of multiple drug resistance microbes has become a global public health problem. The aim of the present investigation was to evaluate possible antibiofilm efficacy of a gallotannin 1,2,6-tri-O-galloyl-β-D-glucopyranose from Terminalia chebula fruits alone and in combination with gentamicin and trimethoprim against preformed biofilms of multidrug-resistant (MDR) uropathogenic E. coli isolates using microbroth dilution, checkerboard titration and kill kinetics methods. Test gallotannin showed > 50% antibiofilm efficacy after 24 h when administered alone whereas gentamicin and trimethoprim failed to do so. But in combination, test gallotannin/gentamicin and test gallotannin/trimethoprim showed 71.24±6.75% and 93.4±8.46% antibiofilm activity respectively. On the basis of FICI values, test gallotannin/gentamicin showed synergistic interactions against 71.42% and test gallotannin/trimethoprim against 85.71% biofilm forming test bacterial isolates. Kill-kinetics study confirmed their synergistic interactions. Thus, gentamicin and trimethoprim in combination with test gallotannin may have potential for treatment of urinary tract infections caused by biofilm forming MDR uropathogenic E. coli

Evaluation of Synergistic Antibacterial and Antioxidant Efficacy of Essential Oils of Spices and Herbs in Combination.

The present study was carried out to evaluate the possible synergistic interactions on antibacterial and antioxidant efficacy of essential oils of some selected spices and herbs [bay leaf, black pepper, coriander (seed and leaf), cumin, garlic, ginger, mustard, onion and turmeric] in combination. Antibacterial combination effect was evaluated against six important food-borne bacteria (Bacillus cereus, Listeria monocytogenes, Micrococcus luteus, Staphylococcus aureus, Escherichia coli and Salmonella typhimurium) using microbroth dilution, checkerboard titration and time-kill methods. Antioxidant combination effect was assessed by DPPH free radical scavenging method. Total phenolic content was measured by Folin-Ciocalteu method. Bioactivity -guided fractionation of active essential oils for isolation of bioactive compounds was done using TLC-bioautography assay and chemical characterization (qualitative and quantitative) of bioactive compounds was performed using DART-MS and HPLC analyses. Cytotoxic potential was evaluated by brine shrimp lethality assay as well as MTT assay using human normal colon cell line. Results showed that among the possible combinations tested only coriander/cumin seed oil combination showed synergistic interactions both in antibacterial (FICI : 0.25-0.50) and antioxidant (CI : 0.79) activities. A high positive correlation between total phenolic content and antibacterial activity against most of the studied bacteria (R2 = 0.688 - 0.917) as well as antioxidant capacity (R2 = 0.828) was also observed. TLC-bioautography-guided screening and subsequent combination studies revealed that two compounds corresponding to Rf values 0.35 from coriander seed oil and 0.53 from cumin seed oil exhibited both synergistic antibacterial and antioxidant activities. The bioactive compound corresponding to Rf 0.35 from coriander seed oil was identified as linalool (68.69%) and the bioactive compound corresponding to Rf 0.53 from cumin seed oil was identified as p-coumaric acid (7.14%) by DART-MS and HPLC analyses. The coriander/cumin seed oil combination did not show any cytotoxic effect both in brine shrimp lethality as well as human normal colon cell line assays. The LC50 in brine shrimp lethality assay was found to be 4945.30 μg/ml and IC50 in human normal colon cell line was > 1000 μg/ml. The results provide evidence that coriander/cumin seed oil combination might indeed be used as a potential source of safe and effective natural antimicrobial and antioxidant agents in pharmaceutical and food industries

Spices and herbs used for the study and yield of their essential oils.

<p>Spices and herbs used for the study and yield of their essential oils.</p

Chemical structure of test gallotannin (1,2,6-tri-O-galloyl-β-D-glucopyranose).

<p>Chemical structure of test gallotannin (1,2,6-tri-O-galloyl-β-D-glucopyranose).</p

Cytotoxic potential of test galloatannin 1,2,6–tri-O-galloyl-β-D-glucopyranose using MTT assay.

<p>Cytotoxic potential of test galloatannin 1,2,6–tri-O-galloyl-β-D-glucopyranose using MTT assay.</p

Relationship between total phenolic content and antibacterial activity of activeessential oils (coriander, cumin and mustard seed oils) against food-borne bacteria.

<p>Relationship between total phenolic content and antibacterial activity of activeessential oils (coriander, cumin and mustard seed oils) against food-borne bacteria.</p

Kill kinetics curves on antibiofilm efficacy of test gallotannin and antibiotics gentamicin and trimethoprim alone and in combination against uropathogenic MDR <i>E</i>. <i>coli</i> biofilms.

<p>[TG: Test gallotannin; GM: Gentamicin; TMP: Trimethoprim].</p

Antioxidant combination effects of active essential oils of spices.

<p>(D)₁ and (D)₂ are the doses of two active essential oils in combination; (Dx)₁ and (Dx)₂ are the doses two active essential oils individually.</p><p>CI <1: synergistic; CI = 1: additive; CI > 1: antagonistic</p><p>Antioxidant combination effects of active essential oils of spices.</p

Efflux-pump inhibitory activity of a gallotannin from <i>Terminalia chebula</i> fruit against multidrug-resistant uropathogenic <i>Escherichia coli</i>

<div><p>This study was carried out to evaluate the possible efflux-pump inhibitory activity of a gallotannin 1,2,6-tri-<i>O</i>-galloyl-β-d-glucopyranose isolated from <i>Terminalia chebula</i> fruit against multidrug-resistant (MDR) uropathogenic <i>Escherichia coli</i>. Susceptibility tests of antibiotics and ethidium bromide in the presence and absence of isolated gallotannin and phenylalanine-arginine β-naphthylamide (PAβN) were conducted by using the microbroth dilution assay. Ethidium bromide accumulation and efflux assays were performed spectrofluorometrically to elucidate the possible resistance-modifying activity of isolated gallotanin, if any. Minimum inhibitory concentrations of test antibiotics and ethidium bromide were reduced in the presence of isolated gallotannin and PAβN. The isolated gallotannin also demonstrated efflux-pump inhibitory activity against the studied bacteria as evidenced from ethidium bromide accumulation and efflux assays. The isolated gallotannin, 1,2,6-tri-<i>O</i>-galloyl-β-d-glucopyranose exhibited efflux-pump inhibitory activity which may be one of the possible mechanisms of its antibacterial action against MDR uropathogenic <i>E. coli.</i></p></div