Characterization of Staphylococcus aureus Isolated from Clinical Specimens by Matrix Assisted Laser Desorption/Ionization Time-of-flight Mass Spectrometry

Abstract Objective To develop a matrix assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) approach to identify Staphylococcus aureus ( S. aureus ) and differentiate methicillin-resistant S. aureus (MRSA) from methicillin-sensitive S. aureus (MSSA). Methods A total of 100 S. aureus strains isolated from clinical specimens and farm workers were collected and analyzed by MALDI-TOF-MS. And data obtained were interpreted with biotyper software. Results Ninety-two strains were identi?ed by MALDI-TOF-MS as S. aureus at a level of secure genus and probable species, and 4 strains were identified at probable genus after their cultivation, spectral collection and data preprocessing. One strain was identified as S. aureus with lower score. It was revealed that identification of S. aureus by MALDI-TOF-MS was highly correlated with typing by biochemical and serological methods with an accuracy as high as 97%. The biotyper cluster analysis showed that 100 isolates were divided into 2 types at the distance level of 400. Higher peak intensity in the mass of both 3784 Da and 5700 Da was observed in MRSA, whereas that was absent from MSSA. Conclusion MALDI-TOF-MS is considered as a simple, rapid and highly reproducible technique with high-throughput and accuracy for the identification of S. aureus and it can reliably differentiate MRSA from MSSA.