In vitro susceptibility testing of cefiderocol in different media of Mueller-Hinton agar

Studying susceptibility to cefiderocol is challenging due to the lack of standardization of culture media.

Susceptibility to cefiderocol was compared using the disk diffusion technique on three commercial Mueller-Hinton agar media and determination of the minimum inhibitory concentration by standard microdilution in Gram-negative isolates that produce metallo-β-lactamase.

There was agreement among all techniques in 58.6% of the isolates. The Becton-Dickinson medium was the most sensitive, and all the three media had the same specificity. The BioMérieux medium was the one that most overestimated resistance, with a higher percentage of major errors. There were no very major errors with any method.

There are differences in interpretation depending on the medium used, so the results should be interpreted cautiously and confirmed with standard microdilution.