Susceptibility testing: accurate and reproducible minimum inhibitory concentration (MIC) and non-inhibitory concentration (NIC) values.
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.
Lambert
R J
RJ
Unilever Research Colworth, Sharnbrook, UK. ronnie.lambert@unilever.com
Pearson
J
J
D000900:Anti-Bacterial Agents / Q000494:pharmacology; D004926:Escherichia coli / Q000187:drug effects; D005026:Ethylene Glycols / Q000494:pharmacology; D008826:Microbial Sensitivity Tests / Q000379:methods*; D009391:Nephelometry and Turbidimetry; D010626:Phenylethyl Alcohol / Q000494:pharmacology; D011549:Pseudomonas / Q000187:drug effects; D011726:Pyridinium Compounds / Q000494:pharmacology; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology; D015203:Reproducibility of Results; D013211:Staphylococcus aureus / Q000187:drug effects; D013997:Time Factors
D000900:Anti-Bacterial Agents; D005026:Ethylene Glycols; D011726:Pyridinium Compounds; D000644:Quaternary Ammonium Compounds; C001524:Laurosept; C005398:phenoxyethanol; D010626:Phenylethyl Alcohol