Susceptibility testing: accurate and reproducible minimum inhibitory concentration (MIC) and non-inhibitory concentration (NIC) values

Abstract

Measuring the minimum inhibitory concentration (MIC) of a substance by current methods is straightforward, whereas obtaining useful comparative information from the tests can be more difficult. A simple technique and a method of data analysis are reported which give the experimentalist more useful information from susceptibility testing. This method makes use of a 100‐well microtitre plate and the analysis uses all the growth information, obtained by turbidometry, from each and every well of the microtitre plate. A modified Gompertz function is used to fit the data, from which a more exact value can be obtained for the MIC. The technique also showed that at certain concentrations of inhibitor, there was no effect on growth relative to a control well (zero inhibitor). Above a threshold value, which has been termed the non‐inhibitory concentration or NIC, growth becomes limiting until it reaches the MIC, where no growth relative to the control is observed.

Assessing the efficacy of zinc oxide nanoparticles against Penicillium expansum by automated turbidimetric analysis

“…Nevertheless, the 10 5 spores/mL concentration showed the lowest variation in most of the cases. The MIC and the NIC of ZnO against P. expansum were determined as they are basic requirements for studying the antimicrobial activity of preservative agents and biocides (Lambert and Pearson 2000). It is demonstrated that the updated version of the LPM (Lambert and Lambert 2003) can be used to process the data obtained from the turbidimetric assay for successfully estimating the MIC and the NIC.…”

“…The updated version (Lambert and Lambert 2003) of the Lambert–Pearson model (LPM) based on a Gompertz function (Lambert and Pearson 2000) was then used to model the observed fractional areas: …”

Synthesis, structure, antimycobacterial and anticancer evaluation of new pyrrolo-phenanthroline derivatives

“…Antimycobacterial activities of the compounds were performed by Center of Tuberculosis Antimicrobial Acquisition and Coordinating Facility (TAACF) at Southern Research Institute [36][37][38] .…”

“…The data from Table 1 illustrate that all tested indolizine with phenanthroline skeleton have a good solubility in microbiological medium, which is quite promising from the pharmacological properties point of view. Then, the IC 50 , IC 90 and MIC of compound were determined by measuring bacterial growth after 5 days in the presence of test compounds [36][37][38]49 . The obtained results are listed in Table 1.…”

Estudos estruturais de enzimas da via de biossíntese de folatos de <i>Xanthomonas albilineans</i> para o desenvolvimento de novos candidatos a agroquímicos para a cultura de cana-de-açúcar

“…Os dados foram ajustados ao modelo matemático descrito pela equação de Gompertz. 101 Os valores da concentração inibitória mínima (MIC) e concentração não inibitória (NIC) foram determinados calculando-se a área fracional sob a curva em função do logaritmo das concentrações dos controles positivos. A área fracional (A fracional ) sob a curva é definida como…”