Agar Diffusion Assays

First of all, the allelopathic activity of a compound (or of a mixture of compounds) isolated as per the above methods should be tested in agar diffusion assays using different algal strains The selection of an assay alga depends primarily on its ability to grow satisfactory under the chosen... 

Since gramicidin is not very soluble in aqueous solution, relatively few agar diffusion assays have been reported. 

Ceriotti has reported an agar diffusion assay for gramicidin utilizing Micrococcus lysodeikticus 1. ... 

Kreuzig has studied the agar diffusion assay for tyrocidine in detail using gel chromatography as an analytical technique146. 

A comparison of the G.L.C. and microbiological (agar-diffusion) assays has been reported by Tsuji et al239 who showed the neomycin content of neomycin sulphate powders determined by the G.L.C. method, to correlate well with values obtained by the microbiological assay when it is assumed neomycin C has 35% of the biological activity of neomycin B. 

Agar diffusion assays using tributyrin, triolein or milk fat. 

A microbiological assay was described for lincomycin in animal feed using an agar diffusion assay and an agar slant of Sarcina Lutea ATCC No. 9341 as the test organism for the analysis of lincomycin (42). 

Food and Drug Administration (FDA) replaced the above mentioned method, " Microbiological agar diffusion assay ", with a microbiological turbidimetric assay because the modified method are more accurate and reliable than agar diffusion assay (43). 

Tamarind fruits are reported to have anti-fungal and anti-bacterial properties (Ray and Majumdar, 1976, Guerin and Reveillere, 1984, Bibitha et al, 2002, Metwali, 2003, and John et al, 2004, all cited in (5)). According to Al-Fatimi and collaborators 11), in an agar diffusion assay, extracts from T. indica flowers showed antibacterial activity against four bacteria tested Staphylococcus aureus, Bacillus subtilis, Escherichia coli and Pseudomonas aeruginosa). Antimicrobial activity of T. indica study has been attributed to lupeol (Ali et al, 1998, cited in 11)). 

Using the same test solutions, both photometric and agar diffusion assays with Staphylococcus aureus and the colorimetric assay of Jones did not show significant potency loss. 

The alcohol 283 and the vinyl compound 113 showed weak activity against Gram-positive bacteria and fungi in an agar diffusion assay (213). No MIC values or organisms were presented. 

For growth bioassays using solid media, modification of the agar diffusion assay used by Flores and Wolk [108] has been shown to provide reliable results [100]. Gross et al. [100] spotted methanol and ethanol extracts on 1% agar plates, dried the extracts in sterile air, and then overlaid the plate with a suspension of indicator cells in 1% agar. After several days of incubation, areas (zones) of no growth were measured and quantification of the inhibitory effects of the test extracts was estimated by comparison with/to the serial dilutions and controls. 

The United States Department of Agriculture (USDA), Eood Safety and Inspection Service (ESIS) developed a bioassay system which incorporates a seven-plate agar diffusion assay that can detect and quantify a range of antibiotic residues found in meat and poultty products. The USDA/FSIS system utilizes bacteria that are relatively sensitive or resistant to a particular class of antibiotic. The bacteria are used in combination with specific antibiotic test agars and four pH-specific, buffered sample extracts. If a detectable antibiotic residue is present in a sample, it produces a zone of clearing (inhibition) on one or more of the test plates. Certain antibiotic residues can be identified according to their characteristic patterns of inhibition. A chart called an antibiogram was developed that depicts expected patterns of inhibition that specific antibiotics are anticipated to produce on the seven plates. 

Agar diffusion assay. Reactivity grades of 0 to 4 determined by extent of degenerated cells in monolayer. Side view shows layers (bottom to top) of cells, agar, and test specimen. 

A very large number of products isolated from fermentation liquors or mycelia of fungi or directly from plants, bulbs and shellfish, have been reported to have antiviral activity. One frequently finds that while a particular compound may appear to have high activity and low toxicity when determined by say an agar diffusion assay, another method of assay will indicate that the compound is highly toxic to cells at low doses. Four su compounds which have been investigated in some detail are ascochlorin (LXVII),... 

Antibiotic assays can be carried out in the form of agar diffusion assays, or as tube assays in liquid media. ... 

Agar diffusion assays were performed to estimate the susceptibility of 11 Staphylococcus aureus and 11 Staphylococcus epidermidis strains. At each of the three concentrations of pDMAEMA tested, Staphylococcus epidermidis was significantly more sensitive than Staphylococcus aureus. Although pDMAEMA (20 mg/ml) partially inhibited the growth of Staphylococcus aureus, such high concentrations are not physiologically relevant [24]. 

An antibacterial active film was developed by lauroyl arginine ethyl ester (LAE)-coating onto a previously corona surface activated PLA film. The presence of anchored LAE molecules was confirmed by scanning electron microscopy (SEM). The antibacterial activity of the LAE/PLA films against Listeria monocytogenes and Salmonella typhimurium was confirmed in vitro by the agar diffusion assay and in vivo on contaminated cooked ham slices. Films also showed their antimicrobial efficiency in the quantitative JIS Z 2801 2000 method of analysis of antimicrobial surfaces. ... 

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