Antimicrobial Screening Tests Research Articles

Evaluation of the Accuracy of Various Disks and Strips for Rapid Culture-Based Gonococcal Antimicrobial Susceptibility Screening Tests in China

PurposeNeisseria gonorrhoeae, resistant to the first-line treatment option ceftriaxone, is widespread in China from 2016. Nowadays, diverse reagents of disks and strips for rapid gonococcal antimicrobial susceptibility tests used in clinics are culture-based disks diffusion and gradient strips methods. This study aimed to evaluate the accuracy, quality, and availability of almost all disks and strips acquired in the Chinese market and serve as a reference for clinical selection.MethodsWe tested the performance of 15 commercial disks and 9 commercial gradient strips acquired in China, compared with traditional agar dilution method. The overall performance was evaluated by the categorical agreement. The reagent accuracy of gradient strips was assessed by the essential agreement.ResultsA total of 167 gonococcal isolates were used to evaluate antimicrobial disks from three brands. The overall categorical agreements were 71.7% to 81.8% for ceftriaxone, less than 58% for cefixime, 100% for spectinomycin, over 98% for ciprofloxacin, below 70.5% for penicillin, and 73.3% to 81.8% for tetracycline. A total of 81 isolates were tested for different gradient strips. Categorical agreements were over 96% for ceftriaxone, 86.2% for azithromycin, 62.3% to 67.1% for penicillin, 41.9% to 67.5% for tetracycline, and 95% for ciprofloxacin. Essential agreements were 57.7% to 87.3% for ceftriaxone, 70% for azithromycin, 64.9% to 68.4% for penicillin, 51.8% to 71.2% for tetracycline, and 91.3% for ciprofloxacin.ConclusionRapid test reagents of disks and strips based on gonococcal culture have suboptimal performance. Disk diffusion for spectinomycin or ciprofloxacin can be recommended for clinical individualized prescription. The gradient strips are of great value to identify ceftriaxone-resistant gonococcal strains. Furthermore, abundant improvements are required for many reagents to further optimize their accuracy till the fulfillment of molecular detection.

Potential of Carvacrol and Thymol in Reducing Biofilm Formation on Technical Surfaces.

Polyvinyl chloride (PVC), polypropylene (PP), polyethylene (PE), and stainless steel (SS) are commonly used in medicine and food production technologies. During contact with microorganisms on the surface of these materials, a microbial biofilm is formed. The biofilm structure is difficult to remove and promotes the development of pathogenic bacteria. For this reason, the inhibition of biofilm formation in medical and food production environments is very important. For this purpose, five naturally occurring compounds were used for antimicrobial screening tests. The two with the best antimicrobial properties were chosen to inhibit the biofilm formation of Staphylococcus aureus and Pseudomonas aeruginosa. After 3 days of exposure, thymol reduced the amount of biofilm of Pseudomonas aeruginosa within the range of 70–77% and 52–75% for Staphylococcus aureus. Carvacrol inhibited the formation of biofilms by up to 74–88% for Pseudomonas aeruginosa and up to 86–100% for Staphylococcus aureus. Those phenols decreased the enzyme activity of the biofilm by up to 40–100%. After 10 days of exposure to thymol, biofilm formation was reduced by 80–100% for Pseudomonas aeruginosa and by about 79–100% for Staphylococcus aureus. Carvacrol reduced the amount of biofilm by up to 91–100% for Pseudomonas aeruginosa and up to 95–100% for Staphylococcus aureus.

Fabrication of penicillin G portable microbiological test plate for on-farm antibiotic residues in milk

Antibiotic residues in animal-derived food products such as milk pose a potential health risk to consumers. A portable antimicrobial screening test plate was fabricated particularly for on-farm testing of milk. A cold-water soluble compound gelling agent composed of guar gum (GG) and konjac glucomannan (KG) was prepared and its properties were optimized for enhancing performance of the test plate. A ratio of 4:6 (GG:KG) showed improved gel strength, cohesiveness, transmittance, and water diffusion of the compound gel. Microbial colony number and size were also increased. The test plate displayed a minimum inhibition concentration of 4 µg/L penicillin G and clearer zone of inhibition. Detection time was also significantly reduced to approximately 9–15 h compared to the conventional agar plate method. The plastic film test plate with optimized compound gel demonstrated tremendous potential for detection of antibiotics in milk.

1,3-Benzoxatiol-2-onas e 1,3-Benzotiazóis como Potenciais Agentes Anticâncer e Antimicrobianos

Over the years, cancer and infectious diseases appear among the leading causes of death worldwide. These data highlight the need for new prototypes to design more potent and selective chemotherapeutics as well as new and non-traditional antimicrobial agents. The main goal of this work was to evaluate some 1,3-benzoxathiol-2-one and 1,3-benzothiazole derivatives for their anticancer, antibacterial and antifungal activities. Derivatives were screened for in vitro anticancer activity against melanoma (SKMEL-19), ascitic fluid (AGP-01) and breast (MCF-7) cancer cell lines by MTT assay. The toxicity profile against erythrocytes and normal cells human fibroblast (MRC-5) was also evaluated. Besides that, in vitro Antimicrobial Screening Test (AST), Minimum Inhibitory Concentration (MIC), Minimum Bactericidal Concentration (MBC) and Minimum Fungicidal Concentration (MFC) assays were performed against Gram-positive and Gram-negative bacteria as well as against Candida species. All tests were performed according to CLSI protocols, using vancomycin, ciprofloxacin and ketoconazole as reference drugs. Derivative 6-methoxy-benzo[d][1,3]oxathiol-2-one ( 7 ) exhibited considerable cytotoxic activity (IC 50 = 3.3 μM) against SKMEL-19 and compound ( E )-4-((2-(benzo[d]thiazol-2-yl)hydrazono)methyl)benzene-1,2,3-triol) ( 16m ) showed good activity against all Candida species (MIC 8-32 µg mL -1 ). The ratio MBC/MIC of 16l and 16m derivatives classified them as bactericidal agents against Gram-positive bacteria. Compound 16 m presented fungistatic profile against Candida albicans and non- albicans species evaluated. Overall, the in vitro results pointed to the potential of derivatives 7 and 16m as new anticancer and antifungal prototypes, respectively, to be further explored as they also presented low toxicity profile.

Metal Chelates of Tridentate (NNO) 1,2,4-Triazine Schiff Base: Synthesis, Physico-chemical Investigation and Pharmacological Screening

Present work portray the synthesis of four new tridentate Schiff base ligand transition metal chelates having 1,2,4-triazine and 1,4-Naphthoquinone as a potential drug candidate, with composition ML2, where M=Co(II), Ni(II), Cu(II) and Zn(II); L = 4-(2-(5,6-diphenyl-1,2,4-triazin-3-yl)hydrazono)-3-hydroxynaphthalene-1(4H)-one (DTN). Credible structure of the synthesized compounds was investigated using different techniques like elemental analysis, molar conductance, mass spectra, magnetic susceptibility, UV–Visible, IR, NMR and TGA. The results were unfailing with tridentate nature of the ligand and octahedral geometry of metal chelates. Thermal scrutiny of the synthesized complexes exemplified absence of coordinated water molecules, decomposition patterns of the complexes and their stabilities. Furthermore, redox behaviour of the synthesized compounds was examined by cyclic voltammetry in DMSO solution. Antimicrobial screening tests played a pivotal role in displaying the presence of metal ion in the ligand system. Chemical nuclease activity was investigated to study the DNA cleavage activities of the synthesized compounds and effectual cleavage was revealed by Co(II) and Cu(II) metal chelates of DTN.

Synthesis, characterization, structural elucidation and biological screening of some bis(diisobutyldithiophosphato)antimony(III) complexes

Seven complexes of type [(C4H9i-O)2PS2]2SbR have been synthesized by the reaction of chlorobis(diisobutyldithiophosphato)antimony(III) with mixed thio and/or oxo donor ligands in 1:1 M stoichiometry, where R = SC6H5, OOCC6H5, SCH2COOH, SOCCH3, OOCCH3, SC6H4COOH and OOC(OH)C6H4. These newly synthesized derivatives have been characterized by different physicochemical (elemental analysis (C, H, S, Sb), melting point, molecular weight determination), spectral (UV, IR, NMR (1H, 13C and 31P)) studies, as well as ESI mass, thermal, powder XRD and biological studies. In the final step of weight loss in thermogravimetric analysis, occurring in the range of 245–505 °C, the degradation of the C6H3CO moieties takes place and antimony sulfide (1/2 Sb2S3) is obtained as remaining material, which is useful in various aspects. Bonded to antimony the diisobutyldithiophosphato substituent behaves as an anisobidentate ligand, which is confirmed through spectral analysis. Powder XRD studies indicate that these compounds crystallize in a monoclinic crystal system with an unit cell volume of ∼7074–7162 Å3 forming nano ranged (9.69–15.69 nm) crystallites. From the antimicrobial screening tests, bis(diisobutyldithiophosphato)antimony(III) thioglycolate (compound 3) has shown a maximum zone of inhibition (19 mm) against E. coli at 200 μg mL−1 concentration.

Synthesis, Characterization and Biological Evaluations of New Imidazo[4,5-a]Acridines as Potential Antibacterial Agents

The significance of bacterial infections and the early success achieved with some antibiotic drugs have prompted the search for new antibacterial agents. Some new derivatives of 3H-imidazo[4,5-a]acridines are introduced as new powerful antibacterial agents against Gram-positive species. The reaction of N-alkyl-5-nitrobenzimidazoles with arylacetonitriles under basic conditions led to the synthesis of 3H-imidazo[4′,5′:3,4]benzo[c]isoxazoles. Rearrangement of the latter compounds in concentrated sulfuric acid containing nitrous acid gave imidazo[4,5-a]acridones. 3H-imidazo[4,5-a]acridines were obtained by reaction of imidazo[4,5-a]acridones in boiling POCl3. Finally, new compounds were synthesized from the reaction of 3H-imidazo[4,5-a]acridine derivatives with aromatic amines in high yields. All new compounds were fully characterized by elemental analysis, IR, NMR and mass spectroscopy data. Antibacterial activity of the new compounds was tested against a panel of strains of Gram-negative and Gram-positive bacteria species and the corresponding minimum bactericidal concentration (MBC) values were determined. Results of the antimicrobial screening tests showed that new compounds are very effective against Gram-positive bacteria and their MBC values are comparable with those of well-known antibacterial agents such as cephalexin.

Mixed arsenic(III) bis(dimethyldithiocarbamato) derivatives with some oxygen and sulfur donor ligands

Seven mixed arsenic(III) bis(dimethyldithiocarbamato) derivatives of type [(CH3)2NCS2]2AsL where, L = OOCC6H5, OOCCH3, OOCC6H4(OH), SC6H5, SCH2COOH, SOCCH3 and S(C6H4)COOH have been synthesized and characterized by various physicochemical [elemental analysis (C, H, N, S & As), molecular weight and melting point determinations], spectral [UV–Vis., FTIR, NMR (1H and 13C)], thermal [TGA and DTG], powder XRD studies. The presence of FT-IR band at 1064–1095 cm−1 due to thiocarbonyl moity and 13C NMR signal in the range 192.56–198.59 ppm due to -NCS2 carbon resonance have indicated anisobidentate mode of bonding of dithiocarbamate group, alongwith this FT far-IR bands observed due to the υ(As–O) and υ(As–S) vibrations in the region 530–532 cm−1 and 302–333 cm−1 respectively, confirm the bonding of arsenic(III) to oxygen and sulfur. Thus, on the basis of results obtained by above spectral techniques, it may be concluded tentatively that, arsenic(III) derivatives (compound 1–7) adopted a distorted octahedral geometry with lone pair of electrons occupying one of the corner of octahedra. Powder XRD studies revealed that these derivatives have nano ranged particle size (5.72 and 16.29 nm) with lower symmetry (monoclinic) crystal system along with unit cell volume (1731 and 1764 Å3). Thermal studies reveal that arsenic(III) bis(dimethyldithiocarbamato) thiosalicylate (compound 7) gives arsenic sulfide as a final decomposition product, which have various potential applications. Antimicrobial screening test showed enhanced activity than free ligands and standard drugs.

Macrocyclic Schiff Base Metal Complexes Derived from Isatin: Structural Activity Relationship and DFT Calculations

Abstract Macrocyclic metal complexes viz., Co(II), Ni(II), Cu(II) and Zn(II) have been prepared using a macrocyclic Schiff base as ligand, which was derived from Isatin, 4-aminoantipyrine and o-phenylenediamine. Further, the complexes have been characterized by elemental analysis, magnetic susceptibility, molar conductance, mass spectrometry, FT-IR-, Far-IR-, UV-Vis-, EDX spectroscopy, 1H NMR and 13C NMR, ESR spectroscopy and SEM. The octahedral geometry of the complexes has been revealed by the spectral data of UV-Vis and ESR as well as by the results of the magnetic susceptibility measurements. Antimicrobial screening tests indicated that the Zn(II) metal complexes showed an excellent antimicrobial activity compared to the other studied metal complexes. The nuclease activity of the metal complexes showed that the Co(II) complex has effectively cleaved DNA. The optimized molecular structure, bond length, bond angle, dihedral angle, chemical reactivity and total energy have been evaluated using the density functional theory (DFT) with B3LYP functional level.

Evaluation of DNA, BSA binding, and antimicrobial activity of new synthesized neodymium complex containing 29-dimethyl 110-phenanthroline

In order to evaluate biological potential of a novel synthesized complex [Nd(dmp)2Cl3.OH2] where dmp is 29-dimethyl 110-phenanthroline, the DNA-binding, cleavage, BSA binding, and antimicrobial activity properties of the complex are investigated by multispectroscopic techniques study in physiological buffer (pH 7.2).The intrinsic binding constant (Kb) for interaction of Nd(III) complex and FS–DNA is calculated by UV–Vis (Kb = 2.7 ± 0.07 × 105) and fluorescence spectroscopy (Kb = 1.13 ± 0.03 × 105). The Stern–Volmer constant (KSV), thermodynamic parameters including free energy change (ΔG°), enthalpy change (∆H°), and entropy change (∆S°), are calculated by fluorescent data and Vant’ Hoff equation. The experimental results show that the complex can bind to FS–DNA and the major binding mode is groove binding. Meanwhile, the interaction of Nd(III) complex with protein, bovine serum albumin (BSA), has also been studied by using absorption and emission spectroscopic tools. The experimental results show that the complex exhibits good binding propensity to BSA. The positive ΔH° and ∆S° values indicate that the hydrophobic interaction is main force in the binding of the Nd(III) complex to BSA, and the complex can quench the intrinsic fluorescence of BSA remarkably through a static quenching process. Also, DNA cleavage was investigated by agarose gel electrophoresis that according to the results cleavage of DNA increased with increasing of concentration of the complex. Antimicrobial screening test gives good results in the presence of Nd(III) complex system.

Antimicrobial activity of new 5-(furan-2-yl)-4-amino-1,2,4-triazole-3-thiol derivatives

The aim of this research was to investigate the antimicrobial activity of some new 5-(furan-2-yl)-4-amino-1,2,4-triazole-3-thiol substituents and in some cases to trace the relationship between activity of compounds and their structure. Research materials and methods. Antimicrobial activity of new 5-(furan-2-yl)-4-amino-1,2,4-triazole-3-thiol derivatives was studied by the method of serial dilutions. The primary antimicrobial activity screening tests of some 5-(furan-2-yl)-4-amino-1,2,4-triazole-3-thiol derivatives have been conducted on standard test cultures of both gram-positive and gram-negative bacteria that belong to clinically significant group of infectious agents with different morphological properties. Staphylococcus aureus ATCC 25923, Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853 were taken as the set of standard test strains. Results and their discussion. The most sensitive strain was a strain of S. aureus ATCC 25923. Extension of alkyl substituents by the Sulfur atom does not lead to gradual changes in activity but the introduction of pentyl radical increases the activity of a molecule in two times. The transition from the S-alkyl derivatives of 5-(furan-2-yl)-4-amino-1,2,4-triazole-3-thiol to 2-((5-(furan-2-yl)-4-amino-1,2,4-triazole-3-yl)-thio)acetic acid esters doesn’t lead to radical changes of antimicrobial activity and is not drawn. But the introduction of isopropyl and isobutyl radicals in the ester structure of these molecules leads to a sharp increase in activity towards S. aureus ATCC 25923. Conclusions. We have explored antimicrobial activity of new 5-(furan-2-yl)-4-amino-1,2,4-triazole-3-thiol alkyl derivatives and 2-((5-(furan-2-yl)-4-amino-1,2,4-triazole-3-yl)thio)acetic acid esters. It was found that all ten compounds exhibit moderate activity. Some influence of studied substituents on the antimicrobial activity results was also found.

Antimicrobial Polyurea: Synthesis, Spectral, and Thermal Overview of Some New Metal Polychelates

ABSTRACTNovel polyureas were synthesized by the addition polymerization of o‐phenylenediamine and toluene 2,4 diisocyanate in 1:1 molar ratio to investigate the biocidal nature of polyurea ligand and its metal polychelates. Some of the transitional metals were allowed to react with this polyurea in 2:1 ligand to metal mole ratio. The successful preparation of polyurea and metal‐containing polyurea was analyzed by elemental analysis and other analytical techniques such as FTIR and 1H NMR. The geometry of metal‐containing polyurea was determined by electronic spectra and magnetic moment measurement. Thermal stability of entire series of synthesized compound was determined by thermogravimetric analysis, and results show that incorporation of metal enhances thermal stability. Microbial actions of the polyurea's were investigated against some bacteria and fungi, namely Staphylococcus aureus, Escherichia coli, and Bacillus subtilis (bacteria), Aspergillus niger, Candida albicans, and Aspergillus flavus (fungi). Antimicrobial screening tests gave good results in the presence of metal ion in the ligand system.

Mixed bis(morpholine‐4‐dithiocarbamato‐S,S′)antimony(III) complexes: synthesis, characterization and biological studies

Some mixed bis(morpholine‐4‐dithiocarbamato‐S,S′)antimony(III) complexes [(OC4H8NCS2)2SbL] with oxygen or sulfur donor ligands [L = ―OOCCH3 (1), ―OOCC6H5 (2), ―SOCCH3 (3), ―SCH2COOH (4), ―OOCC6H4(OH) (5), ―SCH2CH2CH3 (6), ―OC6H5 (7), ½ ―SCH2CH2S― (8)] have been synthesized by reacting the chloro‐bis(morpholine‐4‐dithiocarbamato‐S,S′)antimony(III) with corresponding oxygen or sulfur donor ligands in 1:1 or 2:1 stoichiometries. These have been characterized by melting point, molecular weight determination (cryoscopically), antimony (iodometrically) and sulfur (gravimetrically) estimation, elemental analyses (C, H and N), UV–visible, FT‐IR, far IR, multinuclear NMR (1H and 13C)], TG/DTA analysis, ESI–mass and powder X‐ray diffraction studies. The splitting of the strong band observed at 1046–1066 cm−1 due to υ(C―S) indicated anisobidentate mode of binding of the dithiocarbamate group, which was further supported by a 13C NMR signal appearing at around δ 200 due to NCS2 moiety. The base peak observed at m/z 444.9 supports the strong chelating nature of the morpholine‐4‐dithiocarbamate compared to the other hetero ligands used. TGA revealed that, complexes 21 and 4 were decomposed in three steps; also 6 was decomposed in two steps, followed by the formation of Sb2S3. The results obtained by antimicrobial screening tests indicate that complex 3 showed a maximum zone of inhibition (20 mm) against Trichoderma ressie at a concentration of 200 µg ml−1. Complexes 2, 3 and 8 are most active (zone of inhibition (ZI) 17–20 mm) against both of the fungal species Aspergillus niger and Trichoderma ressie as well as complex 4 (ZI 17 mm) and 6 (ZI 18 mm) against Trichoderma ressie. Copyright © 2014 John Wiley & Sons, Ltd.

Synthesis, Spectral Characterization, and Antimicrobial Activities of Schiff Base Complexes Derived From 4-Aminoantipyrine

ABSTRACT Novel cobalt (II), nickel (II), copper (II), and zinc (II) complexes were synthesized from Schiff base ligand derived from 4-aminoantipyrine, vanillin, and o-anisidine. The structural features were derived from their elemental analysis, molar conductance, magnetic measurements, and various spectroscopic techniques such as infrared, ultraviolet visible, nuclear magnetic resonance, and electron paramagnetic resonance spectroscopy. Antimicrobial screening tests were performed against bacteria and fungi. The comparative study of the minimum inhibitory concentration values of the Schiff base and its metal complexes indicate that the metal complexes exhibit greater antimicrobial activity than the free ligand.

Synthesis of new microbial pesticide metal complexes derived from coumarin-imine ligand

A series of metal complexes of zinc(II), cadmium(II), copper(II), nickel(II) and palladium(II) have been synthesized from coumarin-imine ligand, 8-[(1E)-1-(2-aminophenyliminio)ethyl]-2-oxo-2H-chromen-7-olate, [HL]. The structures of the complexes were proposed in the light of their spectroscopic, molar conductance, magnetic and thermal studies. The ligand coordinated in a tridentate manner through the azomethine nitrogen, the phenolic oxygen and the amine nitrogen and all complexes were non-electrolytes with different geometrical arrangements around the central metal ion. Photoluminescence data unambiguously showed remarkable fluorescence enhancement to Zn2+ over other cations. The antimicrobial screening tests revealed that copper(II) complex exhibited the highest potency and its minimum inhibitory concentration on the enzymatic activities of the tested microbial species was determined. No toxin productivity was detected for all tested toxigenic species upon the exposure of copper complex.

Synthesis, CMC determination, and intercalative binding interaction with nucleic acid of a surfactant–copper(II) complex with modified phenanthroline ligand (dpq)

A surfactant–copper(II) complex, [Cu(dpq)2DA](ClO4)2 (dpq = dipyrido[3,2-d:2′-3′-f]quinoxaline; DA-dodecylamine), was synthesized and characterized on the basis of elemental analyses, UV–vis, IR, and EPR spectra. The critical micelle concentration (CMC) value of this surfactant–copper(II) complex in aqueous solution was found out from conductance measurements. Specific conductivity data at different temperature served for the evaluation of the temperature-dependent CMC and the thermodynamics of micellization (, , and ). In addition, the complex has been examined by its ability to bind to nucleic acids (DNA and RNA) in tris-HCl buffer by UV–vis absorption, emission spectroscopy techniques, and viscosity measurements. The complex has been found to bind strongly to nucleic acids with apparent binding constants at DNA and RNA is 4.3 × 105, 9.0 × 105 M−1, respectively. UV–vis studies of the interaction of the complex with DNA/RNA have revealed that the complex can bind to both DNA and RNA by the intercalative binding mode via ligand dpq into the base pairs of DNA and RNA which has been verified by viscosity measurements. The presence of long aliphatic chain in the surfactant complex increases this hydrophobic interaction. The binding constants have been calculated. The cytotoxic activity of this complex on human liver carcinoma cancer cells was determined by adopting 3-(4, 5-dimethylthiazol-2-yl)-2, 5- diphenyl tetrazolium bromide assay and specific staining techniques. The antimicrobial and antifungal screening tests of this complex have shown good results.

Bahasa Indonesia

Nursery disease frequently found on Acacia crassicarpa seedlings is bacterial leaf blight caused by Xanthomonas sp. Disease symptom starts as a small fleck on the leaf which may then develop to leaf strike or leaf blight if the environmental factors are conducive to disease development. Actinomycetes are soil microorganisms that produce biologically active substances such as enzymes and antibiotics. These compounds could inhibit growth of other microorganisms, particularly bacteria. Thus, Actinomycetes are considered as potential candidates of biocontrol agents for plant pathogens. In the current study Actinomycetes isolated from a wide range of localities were screened for their efficacy against Xanthomonas sp. in vitro. The objective of this study was to obtain Actinomycete isolates effective against Xanthomonas, to mitigate impact of the pathogen on quality of A. crassicarpa seedlings. All Actinomycete collections were isolated from soil by a chain of enrichment isolation procedures. The antibiotic activities were investigated through antimicrobial screening tests using paper discs on assay plates. Of the 75 Actinomycete isolates originally collected and screened, 5 isolates showed good antimicrobial activities against Xanthomonas and are therefore considered as potential biocontrol agent candidates.

Biochemical investigation of yttrium(III) complex containing 1,10-phenanthroline: DNA binding and antibacterial activity

Characterization of the interaction between yttrium(III) complex containing 1,10-phenanthroline as ligand, [Y(phen)2Cl(OH2)3]Cl2⋅H2O, and DNA has been carried out by UV absorption, fluorescence spectra and viscosity measurements in order to investigate binding mode. The experimental results indicate that the yttrium(III) complex binds to DNA and absorption is decreasing in charge transfer band with the increase in amount of DNA. The binding constant (Kb) at different temperatures as well as thermodynamic parameters, enthalpy change (ΔH°) and entropy change (ΔS°), were calculated according to relevant fluorescent data and Vant’ Hoff equation. The results of interaction mechanism studies, suggested that groove binding plays a major role in the binding of the complex and DNA. The activity of yttrium(III) complex against some bacteria was tested and antimicrobial screening tests shown growth inhibitory activity in the presence of yttrium(III) complex.

Binding analysis of ytterbium(III) complex containing 1,10-phenanthroline with DNA and its antimicrobial activity

To evaluate the biological preference of [Yb(phen)2(OH2)Cl3](H2O)2 (phen is 1,10-phenanthroline) for DNA, interaction of Yb(III) complex with DNA in Tris–HCl buffer is studied by various biophysical and spectroscopic techniques which reveal that the complex binds to DNA. The results of fluorescence titration reveal that [Yb(phen)2(OH2)Cl3](H2O)2 has strongly quenched in the presence of DNA. The binding site number n, apparent binding constant K b, and the Stern–Volmer quenching constant K SV are determined. ΔH 0, ΔS 0, and ΔG 0 are obtained based on the quenching constants and thermodynamic theory (ΔH 0 > 0, ΔS 0 > 0, and ΔG 0 < 0). The experimental results show that the Yb(III) complex binds to DNA by non-intercalative mode. Groove binding is the preferred mode of interaction for [Yb(phen)2(OH2)Cl3](H2O)2 to DNA. The DNA cleavage results show that in the absence of any reducing agent, Yb(III) complex can cleave DNA. The antimicrobial screening tests are also recorded and give good results in the presence of Yb(III) complex.

Examining the occurrence of residues of flunixin meglumine in cull dairy cows by use of the flunixin cull cow survey

To determine whether cull dairy cows with signs of certain clinical conditions, termed suspect, are more likely than healthy-appearing cull dairy cows to have violative concentrations of flunixin meglumine in their tissues at slaughter. Cross-sectional study. 961 cull dairy cows. Suspect cull dairy cows were selected from 21 beef slaughter establishments with a high production volume of dairy cows, and kidney and liver tissues were collected for screening. Kidney tissues were screened for antibiotics and sulfonamides with the fast antimicrobial screening test (FAST). Liver tissues were screened for flunixin meglumine with an ELISA, and quantitative analysis of ELISA-positive samples was performed with high-performance liquid chromatography. During the same time period, liver tissues from 251 healthy-appearing cull dairy cows were collected for the Food Safety and Inspection Service National Residue Program Scheduled Sampling Plan, but were screened only for flunixin meglumine. Of 710 suspect cull dairy cows, 50 (7.04%) had liver tissue flunixin concentrations higher than the flunixin tolerance concentration (0.125 ppm). Thirty-one of 168 (18.45%) FAST-positive and 19 of 542 (3.51%) FAST-negative suspect cull dairy cows had violative tissue flunixin concentrations. Two of the 251 (0.80%) healthy-appearing cull dairy cows had violative tissue flunixin concentrations. Suspect cull dairy cows, especially those that were also FAST positive, had a significantly higher incidence of violative tissue flunixin concentrations than healthy-appearing cull dairy cows at slaughter. Targeted sampling plans for flunixin meglumine in suspect dairy cows can help to support more efficient use of resources and further safeguard the nation's food supply.