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Abstract:

Objective To discuss the application of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry（MALDI-TOF MS） in rapid screening of methicillin-resistant Staphylococcus aureus（MRSA）. Methods Thirty strains of MRSA and 29 strains of methicillin-sensitive Staphylococcus aureus（MSSA）were collected and identified by MALDI-TOF MS. The accuracy of the results was compared. The protein peaks of the bacteria were homologically analyzed by MALDI Biotyper software. The protein peak maps were analyzed statistically by ClinProTools 3.0 software,and the protein peaks with statistical difference were chosen to establish the screening model. Eighty clinical isolates of Staphylococcus aureus（40 MRSA and 40 MSSA）were selected to validate the model. Results The accuracy rate of MALDI-TOF MS in the identification of Staphylococcus aureus was above 99.9%. The protein peaks with charge-to-charge ratios of 6 812,17 668,7 594,and 11 990 m/z were the most important characteristic peaks used to distinguish MRSA from MSSA. The receiver operating characteristic （ROC）curve showed that the area under curve（AUC）of the above four peaks was all 1. Gel scan showed that the protein strength of MSSA group in its four peaks was higher than that of MRSA group. The combination of these four peaks was used to screen 80 tested strains,which showed sensitivity of 95.0%,specificity of 82.5%,positive prediction of 84.4% and negative prediction of 94.3%. Conclusion MALDI-TOF is fast,accurate and low-cost in the identification of Staphylococcus aureus. The differential peaks of MRSA and MSSA can be used to identify the two strains quickly,which provides timely and reliable basis for clinical prevention and treatment of MRSA.

Key words: Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, Staphylococcus aureus, Methicillin-resistant Staphylococcus aureus, Methicillin-sensitive Staphylococcus aureus, Screening