Antibiotic Activity of Seven Fungicides against Alternaria panax Whetz

[Objective] This study was conducted to screen suitable fungicides to con-trol ginseng leaf blight caused by Alternaria panax_Whetz. [Method] The antifungal activity of seven fungicides against A. panax_ was determined based on mycelial growth rate in vitro. [Result] The results of in vitro antibiotic activity assay showed that there were significant differences in inhibition rate among different concentration treatments of each of the seven fungicides. Toxicity test results showed that among the seven fungicides, difenoconazole had the smal est EC50 （0.61 mg/L）, fol owed by streptomycin and captan, with EC50 value lower than 100 mg/L. [Conclusion] A fungicide which had strong antifungal activity on A. panax was screened out, and the results wil provide a theoretical basis for further field trial.

Siderophore production from 27 filamentous fungal strains and a novel siderophore with potential biocontrol applications from Aspergillus niger An76

Among 27 filamentous fungi, a strain Aspergillus niger An76 gave the highest siderophore yield even when cultured on natural medium or minimal medium containing 1 mmol L^-1 Fe^3＋. Whereas for most other strains, the capacities of siderophore production was repressed as the concentrations of Fe^3＋ was higher than 20 ~tmol L^-1. Lower ferric iron concentrations were more conducive to siderophore synthesis for those strains. The An76 siderophore was partially purified through a series of chromatography steps using Sephadex LH20 and CM-Sepharose Fast Flow columns. Its structural characteristics differed from typical siderophores, such as catecholates or hydroxamates, and no amino acids or peptide bonds were detected. It may therefore represent a new type of siderophore structure. TBA assay and ESR trapping studies showed that An76 siderophore had remarkable scavenging activity of hydroxyl free radicals in vitro. The antibiotic activities of siderophores produced by An76 were tested against 29 bacterial strains, including plant, animal, and human pathogens. The growth of 14 bacterial strains could be completely inhibited at a siderophore concentration of 8 mg ml^-1 with an incubation time of 30 min. Evidence suggests that the An76 siderophore has potential value as an antioxidant and a biocontrol agent against pathogenic microorganisms.

Antibacterial enhancement of antibiotic activity by Enterolobium contortisiliquum(Vell.)Morong

Objective: To identify the main chemical classes of compounds from aqueous extract of Enterolobium contortisiliquum(E. contortisiliquum) seed bark and to evaluate its antibacterial activity, as well as its potential to increase the activity of antibiotics against strains of Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli.Methods: Different classes of compounds in the aqueous extract of E. contortisiliquum were evaluated based on the visual changes in the coloration and the formation of precipitate after the addition of specific reagents. The antibacterial activity of the extract and its potential to increase of antibiotic activity of antibiotics drugs, gentamicin and norfloxacin was determined by using the microdilution method.Results: Our results demonstrated that the following secondary metabolites were presented in E. contortisiliquum seed bark: flavones, flavonols, xanthones, flavononols,chalcones, aurones, flavones and catechins. The extract itself had very low antibacterial activity against all bacterial strains tested(MIC ≥ 1024 μg/m L), but there was an increase in the antibiotic activity of gentamicin and norfloxacin when combined in the subinhibitory concentration(i.e., MIC/8).Conclusions: Our data suggests that E. contortisiliquum seed bark may be an alternative source for new drugs with the potential to increase antibiotic activity against different strains of bacteria.

Antibiotic Activity of the Essential Oil of Laurel （Laurus nobilis L,） on Eight Bacterial Strains

The recent studies unveil more and more therapeutic properties of the essential oil of Bay leaf （Laurus nobilis L.）. The aim of this study is to determine the chromatographic profile of the essential oil of Bay leaf cultivated under the climatic conditions of the Algerian East and to test its antibiotic activity, against 8 bacterial strains （Escherichia coil, Serratia sp., Proteus sp., Klebsiella pneumoniae, Staphylococcus aureus, Streptococcus D, Pseudomonas aeruginosa and Acinetobacter baumanii）, by using different concentrations. The GC/MS analysis showed that the essential oil is rich in eucalyptol （35.31%）, [3 linalool （22.52%）, eugenol methyl ether （9.17%）, camphene （7.37%） and 3 carene （5.39%）. The antibiotic activity of the essential oil was determined by the diffusion on agar method. Measuring diameters of inhibition method of Vincent [1] indicated that bacterial strains which are very sensitive to even very diluted essential oil are Pseudomonas aeruginosa, Streptococcus D, Serratia sp. and Klebsiella pneumoniae. Staphylococcus aureus, E. coli and Acinetobacter baumanii exhibit less sensitivity and Proteus sp. is especially sensitive to the pure oil. Laurus nobilis L. is a Mediterranean endemic that presents an interesting antibacterial activity and its culture should be encouraged and expanded in Algeria.

Synergistic Effect of Metal Nanoparticles on the Antimicrobial Activities of Antibiotics against Biorecycling Microbes

Biorecycling microbes, which have critical functionalities in natural cycles, are essential to sustain eco-system of the earth. Any alterations in these cycles caused by the mutations of microbes could be a potential threat to life on earth. Antibiotics leached from pharmaceutical waste, animal food and agribusiness prod- ucts are accumulating in the environment. Metal nanoparticles are also accumulating in environment because of their extensive use as biocidal agent in domestic products. Interaction of antibiotics and metal nanoparticles with eco-ffiendly microorganisms has a potential to alter the ecosystem of the earth. In this article, we have studied the antibacterial activities of silver and copper nanoparticles and their for- mulations with antibiotics, tetracycline, and kanamycin against biorecycling microbes, Bacillus subtilis and Pseudomonas fluorescens. Strong synergistic effect of metal nanoparticles on the antimicrobial ac- tivities of commercial antibiotics has been observed. Antimicrobial activity of tetracycline improves by 286%-346% and 0%-28% when being tested in the presence of 250 ppm of silver and copper nanoparticles, respectively. For kanamycin, the improvement is 154%-289% for silver and 3%-20% for copper nanoparticles. Irrespective of the antibiotics and tested organisms, synergy is more prominent for silver nanoparticles even at their minimum active concentration （100 ppm）. This study demonstrates that the combination of metal nanoparticles with antibiotics could be more fatal to ecosystem than either the metal nanoparticles or the antibiotics alone.

Convenient synthesis of urea-linked hydroxyl-alkylamine derivatives of aminoglycosides

A series of urea-linked hydroxyl-alkylamine derivatives of aminoglycosides have been obtained by modification of neamine （1）, kanamycin （2） and ribostamycin （3） at 1, 6＇ and 3 N-sites, respectively, through selective cyclization and nucleophilic ring-opening of cyclic carbamates. All the products showed no noticeable activity in the antibiotic test in vitro. The result suggests that the urea-linked hydroxyl-alkylamine derivatives of aminoglycosides may not be suitable structures for the enhancement of antibiotic activity.

Degradation of kanamycin from production wastewater with high-concentration organic matrices by hydrothermal treatment

It is known that many kinds of fermentative antibiotics can be removed by temperatureenhanced hydrolysis from production wastewater based on their easy-to-hydrolyze characteristics.However,a few aminoglycosides are hard to hydrolyze below 100℃ because of their stability expressed by high molecular energy gap(E).Herein,removal of hard-to-hydrolyze kanamycin residue from production wastewater by hydrothermal treatment at subcritical temperatures was investigated.The results showed the reaction temperature had a significant impact on kanamycin degradation.The degradation half-life(t1/2)was shortened by 87.17-fold when the hydrothermal treatment temperature was increased from 100℃ to 180℃.The t1/2 of kanamycin in the N2 process was extended by 1.08-1.34-fold compared to that of the corresponding air process at reaction temperatures of 140-180℃,indicating that the reactions during hydrothermal treatment process mainly include oxidation and hydrolysis.However,the contribution of hydrolysis was calculated as 75%-98%,which showed hydrolysis played a major role during the process,providing possibilities for the removal of kanamycin from production wastewaters with high-concentration organic matrices.Five transformation products with lower antibacterial activity than kanamycin were identified using UPLC-QTOF-MS analysis.More importantly,hydrothermal treatment could remove 97.9%of antibacterial activity(kanamycin EQ,1,109 mg/L)from actual production wastewater with CODCr around 100,000 mg/L.Furthermore,the methane production yield in anaerobic inhibition tests could be increased about 2.3 times by adopting the hydrothermal pretreatment.Therefore,it is concluded that hydrothermal treatment as a pretreatment technology is an efficient method for removing high-concentration hard-to-hydrolyze antibiotic residues from wastewater with high-concentration organic matrices.