Comparing inactivation protocols of Yersinia organisms for identification with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

RATIONALE: It is recommended that harmful Biosafety Level 3 (BSL-3) bacteria be inactivated prior to identification by mass spectrometry, yet optimal effects of inactivation protocol have not been defined. METHODS: Here, we compare trifluoroacetic acid inactivation (protocol A) with ethanol inactivation (protocol B) of Yersinia organisms prior to identification by matrix-assisted laser desorption/ ionization time-of-flight mass spectrometry (MALDI-TOF-MS). RESULTS: The total number of peaks detected was 10.5 +/- 1.7 for protocol A and 15.7 +/- 4.2 for protocol B (rho < 0.001, ANOVA test). The signal-to-noise ratio for the m/z 6049 peak present in all of the tested Yersinia isolates was 9.7 +/- 3.1 for protocol A and 18.1 +/- 4.6 for protocol B (rho < 0.001). Compared with spectra in our local database containing 48 Yersinia spp., including 20 strains of Y. pestis, the identification score was 1.79 +/- 0.2 for protocol A and 1.97 +/- 0.19 for protocol B (rho = 0.0024). CONCLUSIONS: Our observations indicate that for the identification of Yersinia organisms, ethanol inactivation yielded MALDI-TOF-MS spectra of significantly higher quality than spectra derived from trifluoroacetic acid inactivation. Combined with previously published data, our results permit the updating of protocols for inactivating BSL-3 bacteria. Copyright (C) 2012 John Wiley & Sons, Ltd.