Analysis of methicillin-resistant Staphylococcus aureus major clonal lineages by Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry (MALDI-TOF MS).

Methicillin-resistant Staphylococcus aureus (MRSA) is an important pathogen associated with nosocomial infections in many countries. Multilocus sequence typing (MLST) is one of the genetic typing methods used to type MRSA with a high discriminatory power, however, it is labor-intensive, timely, and costly. Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) coupled with ClinProTools is a potential tool to discover biomarker peaks and to generate a classification model based on highly sophisticated mathematical algorithms to discriminate clonal lineages. We investigated the performance of MALDI-TOF MS for discriminating 154 MRSA-ST239, 72 MRSA-ST5, 30 MRSA-ST59, 14 MRSA-ST45, and 20 MRSA-OST (other clonal lineages). Our results indicate that the model construction and validation have good potency to discriminate ST45 from other lineages with a sensitivity and a specificity of both 100%, and a sensitivity of 95.80% and a specificity of 94.62% to identify ST239. For Biotyper classification, the sensitivity and specificity were more than of 90% for ST239, ST59 and ST45, whereas only 81.94% sensitivity for ST5. By single-peak analysis, the peaks m/z 4808 and 9614 can correctly discriminate ST45 a sensitivity and a specificity of both 100%; the peak m/z 6554 can also discriminate ST239 with a sensitivity of 91.9% and a specificity of 85.4%. In conclusion, MALDI-TOF MS coupled with ClinProTools has a high detection performance for MRSA typing with obvious advantages of being rapid, highly accurate, and being a low cost in comparison with MLST.