Göran Kronvall projects

Research focus of Göran Kronvall projects.

Mini-review on Acridine Orange Staining in Clinical Microbiology

Acridine Orange Staining Review

Antimicrobial susceptibility testing using disc diffusion methods (Göran Kronvall)

Species-related interpretive breakpoints were introduced on a broad scale at the clinical microbiology laboratory in Lund, Sweden, in the late 1970:ies by Göran Kronvall, at that time responsible for clinical bacteriology laboratory services in Lund.

Illustration of Antimicrobial susceptibility testing using disc diffusion methods, E.
Antimicrobial susceptibility testing using disc diffusion methods, E. Photo: Göran Kronvall

Antimicrobial susceptibility testing using disc diffusion methods, E.

NRI - Normalized Resistance Interpretation

Let us ask ourselves: Whick part of an inhibition zone diameter or MIC distribution (species-wise) for a given antimicrobial is unaffected by the development of resistance?

Answer: The high-zone (or the low MIC) side of the most susceptible population of strains, representing the wild-type population. When resistance occurs in an isolate of that species, the position of that isolate in the distribution changes to lower zone sizes or higher MIC values.

So, if we can use the upper zone size slope for a reconstruction of the whole wild-type distribution, then we have obtained an internal calibrator which will enable us to compare results from anywhere, from any laboratory in the world.

This can be done using the Normalized Resistance Interpretation (see link below) method, NRI.

Normalized Resistance Interpretation method, NRI

A summary of the procedure (see link below) is presented in IJAA.

A detailed analysis of parameter setting (see link below) for the NRI calculations was performed by Joneberg et al.

summary of the procedure

analysis of parameter setting

MIC distributions with regular double dilution steps provided too few points for solving the regression, but Etest results (see link below) with intermediate values included, were precise enough for NRI calculations to work. This was shown in studies of tigecycline susceptibility.

Etest results

A patent application for the NRI method has been submitted by Bioscand AB (International Patent Application WO 02/083935 A1).

Normalized Resistance Interpretation method, NRI.

The solution to standardized resistance surveys.


Link to Göran Kronvall bibliography.


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