Method

MIC interpretation, from a raw dilution to an S, I or R your report can carry

The MIC is a measurement. S, I and R are a decision applied to that measurement. Keeping the two apart is what makes a resistance trend readable.

Try the antibiogram builder

Short answer

MIC interpretation is the step that turns a minimum inhibitory concentration into a susceptible, intermediate or resistant category by comparing it against a published breakpoint for that organism and drug. The MIC is what was measured. The category is what someone decided the measurement means, and that decision is revised over time.

Computed from your own isolates, never from a national average.

Dilutions, and why a MIC is rarely an exact number

Broth dilution methods test doubling concentrations, so a reported MIC is the lowest tested concentration that inhibited growth, not a precise value. A result of 4 mg/L means growth was inhibited at 4 and not at 2. Automated systems test an even narrower panel and often infer values in between.

This also produces censored results at the edges of the panel. A report of less than or equal to 0.5 means the true value could be far lower, and greater than or equal to 32 means it could be far higher. Averaging MIC values across isolates without handling censoring produces a number that looks precise and is not.

Why the antibiogram counts categories rather than averaging MICs

A cumulative antibiogram reports the percentage of isolates that were susceptible, not a mean MIC. That is deliberate: percentages survive censoring, panel differences between instruments and the reality that different laboratories test different dilution ranges.

Where MIC values add value is distribution. Watching an MIC distribution creep upward inside the susceptible range is an early signal that a percentage will not show until isolates cross the breakpoint.

Intermediate, SDD and the denominator

Intermediate is not a small amount of resistance. Under EUCAST it means susceptible at increased exposure, and CLSI uses susceptible-dose-dependent for the same idea in specific organism and drug pairs, notably cefepime with Enterobacterales.

For a cumulative report the practical question is the denominator. Counting intermediate as resistant lowers every rate; excluding it from the denominator raises them. Neither is wrong, and both must be stated, which is why it is a visible toggle in the builder rather than a hidden default.

On this site

Every plan and limit is published, with no demo call.

See pricing

The builder runs on a synthetic sample dataset, or on your own CSV, parsed in your browser.

Questions

On this page's topic

Do you need MIC values to build an antibiogram?

No. The S, I and R interpretation is enough. MIC values enable reinterpretation against a different breakpoint version and distribution views.

How do you handle greater-than and less-than values?

They are kept as censored values and never treated as exact numbers. For categorical reporting they are interpreted exactly as reported.

Is disk diffusion supported?

Yes, through the reported interpretation. Zone diameters can be carried as a value, but reinterpretation from zones needs the matching table version for the method used.

See your own resistance picture, cut the way you actually work

Build the antibiogram on the synthetic sample dataset, or drop in your own CSV and watch it parse without leaving your browser. When you want an account, one email address is the whole sign-up.

See the plans and prices

Your file is parsed in your browser and never uploaded. No card required.