Academic literature on the topic 'Agar diffusion assay'

Novel agar diffusion and broth dilution assays were developed for quantitatively estimating the antimicrobial activity of fresh garlic juice. Bacteria found to be inhibited by garlic juice in agar diffusion assay included two gram-positive and five gram-negative species. Leuconostoc mesenteroides was not inhibited. Escherichia coli B-103 (HB101, with pJH101, ampicillin resistant, 100 μg ml−1) was inhibited and chosen as the standard culture for quantitative assays. The agar diffusion assay was based on the slope ratio method, where the slope of dose response for garlic juice was divided by the slope of dose response for methylmethane thiosulfonate (MMTSO2). Juice from fresh garlic varied in activity between 1.76 and 2.31 μg of MMTSO2 per mg of garlic juice. The activity of juice decreased during 11 months of storage of garlic cloves at 5°C from 2.31 to less than 0.1 μg of MMTSO2 per mg of juice. The broth dilution assay also used the E. coli B-103 culture, which permitted selective enumeration of this bacterium when 100 μg ml−1 of ampicillin was incorporated into the enumerating agar. Selective enumeration was essential since the garlic juice was not sterile and, thus, contained natural flora. Growth of E. coli was unaffected by 0.1%, delayed by 0.25%, and completely inhibited at 0.5 and 2% garlic juice in broth during 24 h of incubation at 37°C. The minimum inhibition concentration of garlic juice by broth dilution assay was, thus, estimated to be 0.5%, which is equivalent to 3.46 μg of MMTSO2 per mg of garlic juice by the agar diffusion assay.

The improved agar diffusion method for determination of residual antimicrobial agents was investigated, and the sensitivities of various combinations of test organisms and assay media were determined using 7 organisms, 5 media, and 31 antimicrobial agents. Bacillus stearothermophilus and synthetic assay medium (SAM) showed the greatest sensitivity for screening penicillins (penicillin G and ampicillin). The combination of Bacillus subtilis and minimum medium (MM) was the most sensitive for tetracyclines (oxytetracycline and chlortetracycline), B. stearothermophilus and SAM or Micrococcus luteus and Mueller-Hinton agar (MHA) for detecting tylosin and erythromycin, B. subtilis and MHA for aminoglycosides (streptomycin, kanamycin, gentamicin, and dihydrostreptomycin), B. stearothermophilus and SAM for polyethers (salinomycin and lasalocid), and B. subtilis and MM or Clostridium perfringens and GAM for polypeptides (thiopeptin, enramycin, virginiamycin, and bacitracin). However, gram-negative bacterium Escherichia coli ATCC 27166 and MM were better for screening for colistin and polymixin-B. For detecting the synthetic drugs tested, the best combination was B. subtilis and MM for sulfonamides, E. coli 27166 and MM for quinolones (oxolinic acid and nalidixic acid), B. subtilis and MM for furans (furazolidone), and the bioluminescent bacterium Photobacterium phosphoreum and luminescence assay medium for chloramphenicol and oxolinic acid. The results showed that the use of four assay plates, B. stearothermophilus and SAM, B. subtilis and MM, M. luteus and MHA, and E. coli 27166 and MM, was superior to the currently available techniques for screening for residual antimicrobial agents in edible animal tissues.

Antibiotics production is the most emerging field worldwide with a constant need for the new ones to fight the microbial resistance. In this context, the research was pursued to isolate, characterize and screen for promising antibiotic-producing microbes from local soil. The soil bacterial isolates (S1, S2, S3,S4, and S5) and fungal isolates (F1, F2, F4, F6, and F7) were selected and screened for antimicrobial activity against the Test bacteria by agar well diffusion and disc diffusion methods. Assays for Extracellular enzymes including Protease, Lipase, Lecithinase, Cellulase, and Amylase following the substrate hydrolysis were performed on different Agars such as Casein Agar, Tween 80 Agar, Egg Yolk Agar, Carboxymethylcellulose Agar, and Starch Agar respectively. The isolated microorganisms which produced antimicrobial compounds were identified as Bacillus, Actinomycetes, Streptomycetes, H. werneckii, A. niger, A. flavus, A. fumigatus and P. notatum on the basis of their cultural and microscopic characteristics and their optimum growth. The antimicrobial activity was determined by varying pH and NaCl concentrations. The research work revealed that among all isolates Actinomycetes (21%), P. notatum (29%) and H. werneckii (21%) showed maximum bioactivities against the test organisms and all isolates exhibited at least four of the tested enzymes.

Abstract The agar diffusion method, widely used in antibiotic dosage, relates the diameter of the inhibition zone to the dose of the substance assayed. An experimental plan is proposed that may provide better results and an indication of the assay validity. The symmetric or balanced assays (2 2) as well as those with interpolation in standard curve (5 1) are the main designs used in the dosage of antibiotics. This study proposes an alternative experimental design for erythromycin microbiological assay with the evaluation of the validation parameters of the method referring to linearity, precision, and accuracy. The design proposed (3 1) uses 3 doses of standard and 1 dose of sample applied in a unique plate, aggregating the characteristics of the 2 2 and 5 1 assays. The method was validated for erythromycin microbiological assay through agar diffusion, revealing its adequacy to linearity, precision, and accuracy standards. Likewise, the statistical methods used demonstrated their accordance with the method concerning the parameters evaluated. The 3 1 design proved to be adequate for the dosage of erythromycin and thus a good alternative for erythromycin assay.

Gramicidin, an antimicrobial peptide active against Gram positive bacteria, is commonly used in pharmaceutical preparations for topical use. Considering that only the turbidimetric method has been described in the literature, the present study sought to develop and validate an agar diffusion method for the dosage of gramicidin. The method was developed and validated using the Kocuria rhizophila ATCC 9341 as a test microorganism. Two designs were used: a 3x3 parallel-line model, and a 5x1 standard curve. The validation demonstrated that the method follows the linear model (r²= 0.994), presenting a significant regression between the zone diameter of growth inhibition and the logarithm of the concentration within the range of 5 to 25.3 µg/mL. The results obtained for both designs were precise, having a relative standard deviation (R.S.D.) for intra-day precision of 0.81 for the 3x3 assay and 1.90 for the 5x1 assay. For the inter-day precision, the R.S.D. was 1.35 for the 3x3 and 2.64 for the 5x1. The accuracy was verified and results confirmed to be accurate, having a tolerance interval of 95%, which lay within permitted limits and appropriate trueness. In addition, the method was considered selective, with limit of detection and upper and lower limits of quantification of 2.00, 5.00 and 25.3 µg/mL, respectively. No difference in precision between the designs used in the agar diffusion method was evident (p>0.05). The method proved to be appropriate for the microbiological dosage of the raw material gramicidin.

Abstract As a prerequisite to validation of the cylinder plate diffusion assay for the antibiotic colistin sulfate in plasma, the assay needed to be optimized. Bordetella bronchiseptica (ATCC 4617) was the test organism for optimization. Ionic strength of buffer, quantity of test organism, duration of prediffusion, and volume of agar layer were studied. The effects of each factor were examined according to an experimental design. A 4 h prediffusion at 4°C increased sensitivity. Repeatability was improved by using 100 mL agar per bioassay dish, dilution of the plasma with buffer (3 + 1), and prediffusion. The slope of the standard response line was steeper with prediffusion. The reduced quantity of test organism contributed to better sensitivity and good repeatability. No significant interaction between these factors was found. Experimental designs were used successfully to rapidly set up a microbial method requiring a limited number of runs

As proteínas inibidoras de poligalacturonases (PGIPs) presentes na parede celular são capazes de limitar o potencial destrutivo da poligalacturonase (PG) fúngica e, assim, constituem um tipo importante dentre os diversos sistemas de defesa do tecido vegetal frente à infecção fúngica. No mamão, o ataque fitopatogênico é o principal causador de danos pós-colheita, e sua alta susceptibilidade pode estar relacionada com a baixa eficácia ou pouca abundância dos meios de defesa anti-fitopatogênica. Uma vez que isso pode estar relacionado com as PGIPs e nada se conhece sobre o papel dessas proteínas nesse fruto, o objetivo do trabalho foi clonar os genes das PGIPs de mamoeiro e definir seu padrão de expressão em diferentes órgãos e tecidos e ao longo do amadurecimento. Para tanto, foram identificadas no genoma do mamoeiro, a partir de critérios que definem a identidade de uma PGIP, duas prováveis sequências dentre 13 candidatas iniciais. Ambas foram clonadas a partir das sequências genômicas e de cDNA, sequenciadas e sua identidade confirmada, sendo denominadas Cppgip4 e Cppgip6. As análises de expressão relativa em diversos tecidos e idades fisiológicas do mamoeiro demonstraram que os dois genes apresentaram diminuição da expressão com o desenvolvimento dos frutos, sendo que com a polpa apresentou redução dos níveis de expressão relativa de Cppgip4 em até 18 vezes dos 30 dias pós-antese (DPA) ao 9 dias pós-colheita (DPC). Na casca também houve redução significativa da expressão com o desenvolvimento. Para a expressão absoluta, nos frutos, sementes, caules, raízes e folhas, o número de cópias de ambos os transcritos decresceu com o desenvolvimento, sendo cerca de cem mil vezes mais abundante para Cppgip6 que para Cppgip4. As tentativas de expressão de proteínas recombinantes em Pichia pastoris não geraram resultado positivo, provavelmente em virtude das condições ideais de indução ainda não terem sido estabelecidas corretamente para o ensaio. A atividade de PGIPs extraídas diretamente do tecido foi medida por análise de difusão em ágar empregando pectinase de Aspergillus niger e revelou uma tendência à diminuição da porcentagem de inibição à medida que os frutos se desenvolveram, em concordância com os resultados da análise por qPCR. O conjunto de resultados sugere que a expressão varia com o estádio de desenvolvimento do fruto e é tecido-específica, possivelmente em resposta à diferente susceptibilidade dos tecidos ao ataque fitopatogênico, indicando que menores níveis de transcritos e atividade no amadurecimento, período de maior susceptibilidade, poderiam sinalizar para a regulação do processo degradativo marcando o início da senescência.
Polygalacturonase inhibiting proteins (PGIPs) present in plant cell walls are able to inhibit the destructive action of fungal polygalacturonase (PG). In this way, they constitute an important type of plant defense system against fungal infections. In papaya fruit, the pathogenic attack is the main cause of post harvesting loss, and its high susceptibility may be related to the low efficiency or low abundance of anti-phytopathogenic defense. Since this fact could be related to PGIPs expression and little is known about the response of these proteins in the fruit, the aim of the present work was to clone the genes of PGIPs papaya fruit and set their expression pattern in different organs and tissues throughout fruit ripening. Thus, two probable PGIP sequences among 13 initial candidates were identified in the papaya genome by using specific criteria. Both sequences were cloned from cDNA and genomic samples, sequenced and confirmed its identity, and then being named Cppgip4 and Cppgip6. Analysis of relative expression in various tissues at different physiological stages demonstrated that both genes were down regulated during fruit development. The relative expression levels of Cppgip4 in papaya pulp was reduced by 18 times from the 30 days post-anthesis (DPA) to the 9 days post-harvest (DPH). Similarly, gene expression in papaya peel was significant down regulated during fruit development. Absolute expression analysis revealed gene expressions in the fruit pulp, seed, stem, root and leaf were also down regulated within development. Moreover, Cppgip6 gene expression was a hundred thousand times more abundant than Cppgip4. The recombinant protein expression in Pichia pastoris did not result positive, probably because of the ideal conditions of induction have not been properly established the yet. The activity of PGIPs extracted directly from the tissue was measured by the agar diffusion assay using pectinase from Aspergillus niger and showed decrease of inhibition during fruit developed in accordance with the results of the qPCR analysis. Based on the results it is possible to suggest the expression of these genes varies temporally with the developmental stage of the fruit and is tissue-specific, possibly in response to the different susceptibility of tissues to pathogenic attack. In addition, the lowest levels of PGIP expression were achieved at the fruit ripening, when the susceptibility to fungal infection is high and could signal for regulating the degradation process characterized by the onset of senescence.

Itraconazole is a triazole antifungical agent with a broad spectrum of activity belonging to the class of azole, indicated in the treatment of different types of mycotic infections systemic and local. Its mechanism of action is based on the ability to inhibition of synthesis of ergosterol which is a component of vital importance to the cell membrane of the fungi. This drug has only official methodology for raw material, described in British and European Pharmacopeia. In this paper, following the main guidelines for validation, were developed and validated quantitative analytical methods that can be applied both for the raw materials as the finished product containing itraconazole capsules through a high performance liquid chromatography (HPLC) with detection in the ultraviolet (254 nm, C8 reversed-phase column, mobile phase acetonitrile : water (65:35), the temperature of 25 °C) and microbiological assay by agar diffusion, with planning 3x3, employing Candida Albicans ATCC 10231 as microorganism testing in the culture medium antibiotic N° 19 in the region of the ultraviolet spectrophotometry (256 nm, with final solutions in 0.1 mol l-1 hydrochloric acid). All methods showed appropriate linearity, precision, accuracy, robustness and specificity.
O itraconazol é um antifúngico triazólico de amplo espectro de ação pertencente à classe dos azóis, indicado no tratamento de diferentes tipos de infecções micóticas sistêmicas e superficiais. Seu mecanismo de ação baseia-se na capacidade de inibição da síntese do ergosterol que é um componente de vital importância para a membrana das células dos fungos. Este fármaco possui metodologia descrita, somente, para matéria-prima, que se encontram oficializadas nas Farmacopéias Britânica e Européia. Neste trabalho foram desenvolvidos e validados, em conformidade com guias nacionais e internacionais, métodos analíticos quantitativos que podem ser empregados tanto para matéria-prima quanto para forma farmacêutica de cápsulas contendo itraconazol. Utilizaram-se as metodologias: cromatografia a líquido de alta eficiência (CLAE) com detecção na região do ultravioleta (UV) em 254 nm, coluna de fase reversa C8, fase móvel acetonitrila : água (65:35), na temperatura de 25 °C; Ensaio microbiológico por difusão em ágar com planejamento 3x3, empregando Cândida Albicans ATCC 10231 como microrganismo teste em meio de cultura antibiótico n°19 e Espectrofotometria na região do ultravioleta, no comprimento de onda de 256 nm , com soluções finais em ácido clorídrico 0,1 mol.l-1 . Todos os métodos apresentaram linearidade, precisão, exatidão, robustez e especificidade adequados.

Indiana University-Purdue University Indianapolis (IUPUI)
Resilon is a resin-based obturation material that claims to create a monoblock through bonding of RealSeal sealer to the dentin walls and to the core material. Resilon is comprised of a biodegradable polymer, polycaprolactone, and inorganic fillers. Resilon has been shown to undergo enzymatic hydrolysis by bacterial enzymes such as lipase. This study aims to demonstrate if bacteria found within the infected root canal system are capable of degrading Resilon utilizing an agar disc hydrolysis method. A 0.1-percent Resilon emulsion and a gutta-percha emulsion were prepared with Tryptic Soy Agar in plates. Several bacterial species were inoculated in eight spots each on the Resilon and gutta-percha agar plates and the plates were observed for the formation of hydrolytic halos surrounding bacteria signifying their ability to degrade the material. The bacterial enzyme Lipase PS served as a positive control. P. intermedia, P. aeruginosa, P. assacharoylitica, S. epidermidis and S. aureus all demonstrated hydrolytic halos, clear zones, at each of the eight inoculation locations (100%, 95%CI 63%-100%) on the Resilon plates. The halos were similar to those seen in the positive lipase control. No halos were seen with E. faecalis, F. nucleatum, S. mutans, S. sanguis, or P. gingivalis at any of the eight inoculation spots (0%, 95%CI 0%-37%) on the Resilon plates. No hydrolytic halos were seen around any bacterial colonies or the Lipase PS on the gutta-percha plates. The results of this study indicate that bacteria found in endodontic infections can hydrolize Resilon dispersed into an emulsion. The potential exists for Resilon degradation after its use as an obturation material in infected root canal systems. Given that root canal therapy does not render a canal void of microorganisms, it is prudent to obturate the root canal system with a material that cannot be degraded by bacteria and their enzymes.

Thesis (M.Tech.: Homoeopathy) - Dept. of Homoeopathy, Durban Institute of Technology, 2003 xviii, 122 leaves
This study was designed to investigate the antimicrobial efficacy of Withania somnifera and Xysmalobium undulatum plant tinctures in 62% ethanol in inhibiting the in vitro growth of Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus.

The utilization of in vitro tests with a tiered testing strategy for detection of mild ocular irritants can reduce the use of animals for testing, provide mechanistic data on toxic effects, and reduce the uncertainty associated with dose selection for clinical trials. The first section of this thesis describes how in vitro methods can be used to improve the prediction of the toxicity of chemicals and ophthalmic products. The proper utilization of in vitro methods can accurately predict toxic threshold levels and reduce animal use in product development. Sections two, three and four describe the development of new sensitive in vitro methods for predicting ocular toxicity. Maintaining the barrier function of the cornea is critical for the prevention of the penetration of infections microorganisms and irritating chemicals into the eye. Chapter 2 describes the development of a method for assessing the effects of chemicals on tight junctions using a human corneal epithelial and canine kidney epithelial cell line. In Chapter 3 a method that uses a primary organ culture for assessing single instillation and multiple instillation toxic effects is described. The ScanTox system was shown to be an ideal system to monitor the toxic effects over time as multiple readings can be taken of treated bovine lenses using the nondestructive method of assessing for the lens optical quality. Confirmations of toxic effects were made with the utilization of the viability dye alamarBlue. Chapter 4 describes the development of sensitive in vitro assays for detecting ocular toxicity by measuring the effects of chemicals on the mitochondrial integrity of bovine cornea, bovine lens epithelium and corneal epithelial cells, using fluorescent dyes. The goal of this research was to develop an in vitro test battery that can be used to accurately predict the ocular toxicity of new chemicals and ophthalmic formulations. By comparing the toxicity seen in vivo animals and humans with the toxicity response in these new in vitro methods, it was demonstrated that these in vitro methods can be utilized in a tiered testing strategy in the development of new chemicals and ophthalmic formulations.