Thank you for your feedback

As far as I understand, the minimum value of MIC to consider a molecule active is relative depending on the type of bacteria

I can not understand your point.

In my knowledge it depends on many factors, and most important factor is toxicity of your agent.

You have to consider pharma characters and get advice from expert persons in this field.

Good luck.

There are standard concentrations of antibiotic which can differ for each organism. These are govered by the European Committee on Antimicrobial Susceptibility Tests (EUCAST) which provide breakpoint tables for interpretation of MICs and zone diameters in antimicrobial assays. Version 8.0, 2018. can be found at http://www.eucast.org. Many of the factors are standardised to enable comparisons such as media etc . There are also standard type strains that you can also test the antibiotics against and your own strains.

Thank you Gerry Quinn for your help

Dear Doctor

Go To

The Minimum Inhibitory Concentration of Antibiotics: Methods, Interpretation, Clinical Relevance

Beata Kowalska-Krochmal* and Ruth Dudek-Wicher

Pathogens. 2021 Feb; 10(2): 165.

Published online 2021 Feb 4. doi: 10.3390/pathogens10020165

[The use of MIC value in treatment, based on individually defined PK parameters can significantly improve the effectiveness of antibiotic therapy. Although, the methodology for the determination of these parameters is very difficult and not even accessible to doctors, the PK/PD parameters can be estimated using the Monte Carlo method. Such a solution was proposed by EUCAST, to evaluate the achievement of PK/PD index depending on the MIC and antibiotic dose of known PK. In addition, recently, EUCAST, by introducing two susceptibility categories, has clearly made dose volume and road of administration depend on MIC values. The possibility to use the MIC values to increase the probability of therapeutic success can therefore be easier to implement. However, this does not change the fact that the attempt of determining this value in a microbiological laboratory is difficult due to methodology recommended by EUCAST and CLSI. According to these institutions, the most reliable is the broth microdilution method, a manual, demanding and time-consuming procedure. It should also be underlined that sometimes the information about susceptible strain, which is a result of even as precise value as the MIC, does not necessarily have to be true. It is known that bacteria have mechanisms that are impossible to detect in laboratory routine such as heterogeneous resistance, tolerance or persistence. Unfortunately, this feature of micro-organisms can contribute to the treatment failure, despite the optimal choice of antibiotic therapy.]

Dear Doctor

Go To

When and How to Use MIC in Clinical Practice?

by Sophie Magréault, Françoise Jauréguy,

Etienne Carbonnelle, Jean-Ralph Zahar

Antibiotics 2022, 11(12), 1748; https://doi.org/10.3390/antibiotics11121748

[Conclusions

The microbiological and pharmacological tools already available are useful for the treatment optimization and follow-up of serious infections. The implementation of these tests depends on a number of criteria that we tried to list without being exhaustive . We particularly recommend the determination of MIC when organisms have a high level of resistance, when patients present a risk of under-exposure, and in the case of difficult-to-access infections . Furthermore, practitioners should not hesitate to use MIC and TDM more widely, without waiting for the appearance of adverse effects or the absence of clinical improvement, especially when the antibiotic chosen is not the best available treatment. In the future, yielding the MIC in less than 24 h and software helping to optimize administration will increase therapeutic adequacy and probably patient survival. Nevertheless, PK-PD data are and will remain tools at the disposal of the clinician, and the patient’s clinical progress is still the most important guide for dose adjustment.]