Rapid Identification and Methicillin Resistance Test to Staphylococcus aureus in Cerebrospinal by MALDI-TOF MS

Background: Bacterial meningitis is a disease with high mortality and morbidity, and it primarily manifests as symptoms involving the central nervous system (CNS). Hence, it would be of great importance to make an early diagnosis and initiate empirical antimicrobial treatment in time for this disease. Methods: In this study, we investigated the feasibility of rapid pathogen identification and drug resistance analysis through the combination of centrifugation-based enrichment of bacteria and matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS). Specifically, the cerebrospinal samples were treated by differential centrifugation to collect precipitates after a short-term rapid culture. Then, the precipitates were identified by MALDI-TOF MS. Subsequently, the bacterial solution (106 CFU/mL) was mixed with an equal volume of cation-adjusted Mueller-Hinton broth (CAMHB) supplemented with cefoxitin (4 µg/mL). After the culture of the mixture, the precipitates obtained by centrifugation were analyzed by MALDI-TOF MS. Results: The efficiency of centrifugation-based enrichment of Staphylococcus aureus (S. aureus) was 87.9% at 103 CFU/mL and increased to 90.4% at 102 CFU/mL. This identification efficiency reached 100% after an 8-hour culture. The optimal testing time for bacterial resistance identification was achieved by the culture within 3 hours. The validity, sensitivity, and specificity were all 100% at this time point. The results of the rapid identification method were identical to those of the broth microdilution method. Conclusion: Through this protocol, the identification and drug resistance analysis of S. aureus in the cerebrospinal fluid (CSF) can be completed within 11 hours. These findings are expected to provide a new method for the rapid diagnosis and treatment of patients with bacterial meningitis.