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Insufficient repeatability and reproducibility of MALDI-TOF MS-based identification of MRSA

Publication at Faculty of Medicine in Pilsen, Faculty of Medicine in Hradec Králové |
2020

Abstract

Rapid identification of methicillin-resistantStaphylococcus aureus(MRSA) is essential for proper initial antibiotic therapy and timely set up of hygienic measures. Recently, detection of MRSA using MALDI-TOF mass spectrometer mediated by the peptide-phenol-soluble modulin (PSM-mec)-linked to the class Amecgene complex present in SCCmeccassettes types II, III, and VIII of MRSA strains, has been commercially available.

We present here a multicentre study on MALDI-TOF MS detection of MRSA evincing a poor repeatability and reproducibility of the assay. The sensitivity of the assay varies between 50 and 90% in strains carryingpsm(MEC)andpsm(delta)genes encoding for PSM-mec and delta-toxin (a member of the PSM peptide family), respectively.

No false positive results were found. The very major error calculation was 30% and the major error achieved 0%.

Interlaboratory repeatability varies between 0 and 100%. No significant difference was observed with the use of different cultivation media.

Our data showed a poor sensitivity of the method excluding it from the use in routine laboratory testing.