Dilution assay

Antibacterial Activity of Seaweeds and their Extracts

Published in Leonel Pereira, Therapeutic and Nutritional Uses of Algae, 2018

Leonel Pereira

MIC represents the lowest concentration of crude or purified algal extracts that inhibit the bacterial or fungal growth (Silva 2015). The concentration serial broth (micro) dilution assay has been used in several studies (Hellio et al. 2001, Bazes et al. 2009, Boisvert et al. 2015). Minimum inhibitory concentration for the extracts of algae are usually determined by broth microdilution method, according to procedures described in the reference document M07-A10 of Clinical and Laboratory Standards Institute (CLSI 2015), with some modifications. This approved guideline addresses methods for dilution of antimicrobial susceptibility testing for bacteria that grow aerobically (Silva 2015).

Published in Ronald M. Atlas, James W. Snyder, Handbook Of Media for Clinical Microbiology, 2006

Ronald M. Atlas, James W. Snyder

Use: For antibiotic assay testing. Used for the serial dilution assay of penicillins and other antibiotics. Used in the turbidimetric assay of penicillin and tetracycline with Staphylococcus aureus. For the cultivation and maintenance of Staphylococcus aureus.

Formulating the prion hypothesis

Published in Kiheung Kim, The Social Construction of Disease, 2006

Kiheung Kim

This problem of inaccuracy being caused by uncontrolled variables seems to be widely accepted. Even Richard Race in RML, a former Prusiner collaborator in the 1970s, pointed out that where a linear curve between dose and incubation time obtained, then the method would be fine. But if a non-linear curve was established, it would not be possible to interpret what is going on (Race 2000). From these arguments, it can be summarised that Prusiner's novel method may be effective with respect to saving time and money, but that caution needs to be exercised when judging the accuracy of the results. However, Byron Caughey, who is a biochemist in RML, argues that the method is acceptable where fairly rough-and-ready estimates of infectivity performed under standardised conditions will suffice: It all depends on the kind of information that we need. If we need a quantitative assessment, a quantitative comparison of the amount of infectivity there, we prefer the endpoint dilution assay, though it is much more expensive and time consuming. The incubation time assay can be helpful and useful under certain circumstances, where you have a very well established standard curve between the actual endpoint dilution titer and the incubation period. But any time you are crossing species barriers or permuting the agents or manipulating it so that you create a different set of conditions or you are working in a different species, or anything like that where the standard curve may not work anymore; or you simply manipulated your samples in certain ways, biochemically, so that you don't know if the standard curve applies any more, you have to go back to the endpoint dilution assay. So, as often as possible, when it is really critical to get a quantitative comparison of titers, for whatever purpose, we prefer to use the endpoint dilution.(Caughey 2000c)

The effect of transferrin-targeted, resveratrol-loaded liposomes on neurosphere cultures of glioblastoma: implications for targeting tumour-initiating cells

Published in Journal of Drug Targeting, 2019

Aditi Jhaveri, Ed Luther, Vladimir Torchilin

To determine if free RES can inhibit the TICs, its ability to inhibit the anchorage-independent growth of NS was studied. LN-18 NS which were originally derived from the limiting dilution assay were used to test RES concentrations from 20 to 80 µM . On day 8, the NS were imaged to determine the effects of RES on their growth. Whole wells containing LN-18 NS with various RES concentrations are shown in Supplementary Figure S3. Figure 5(A) shows the representative images from each well. It was clear that RES had a significant dose-dependent effect on the growth of NS. Both the number and size of the NS decreased with increasing RES concentrations. In the control well (no RES) as well as the DMSO group, the NS were larger and in greater numbers than in the RES-treated wells. The effects on NS growth inhibition were evident even at the lowest RES concentration (20 µM), with the highest concentration (80 µM) completely inhibiting the NS growth. There was a complete absence of cell colonies at the highest concentration of RES.

Reproducibility between two readout methods of a commercial broth microdilution assay for Pseudomonas aeruginosa isolates from patients with Cystic Fibrosis

Published in Infectious Diseases, 2019

Bas T. Franssens, Ad C. Fluit, Rob J. Rentenaar

Sixty-one stored P. aeruginosa isolates, obtained from respiratory secretions of CF patients collected at the University Medical Center Utrecht, the Netherlands (one isolate per patient), were thawed. After thawing, identity of P. aeruginosa was reconfirmed for all isolates (for details, see Supplementary information). Isolates with no growth in positive control wells of the broth dilution assay after 24 h incubation were excluded (n = 5), because the 24 h reading results are invalid and cannot be compared to the 48 h reading results. In 2/5 isolates, 48 h prolonged incubation did not result in readable results. In 3/5 isolates only faint growth was observed in the positive control wells after 48 h. All isolates (n = 56) were phenotypically characterized when grown on Luria-Bertani agar and growth rate was assessed using a Bioscreen C™ device (Turku, Finland) [8,9].