lesson learned in bacterial identification using maldi-tof zybio exs2600

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (maldi-tof ms) has emerged as a rapid and reliable method for bacterial identification, offering advantages in speed, accuracy, and broad microbial coverage, including gram-positive, gram-negative, and fungal species. however, discrepancies between maldi-tof and conventional biochemical identification methods have been reported, often attributed to preanalytical and analytical variables. this study aimed to analyze the impact of sample preparation on the accuracy of bacterial identification using maldi-tof zybio exs2600. a descriptive observational study was conducted from january to june 2024 at the microbiology laboratory of ibnu sina hospital, gresik, indonesia. a total of 77 bacterial isolates from blood, urine, sputum, and other clinical specimens were included. all isolates had previously been identified using bd phoenix m50 and were re-identified using maldi-tof after preparation with formic acid, acetonitrile, and α-cyano-4-hydroxycinnamic acid as matrix. discrepancies in identification were observed in 24 out of 77 samples (31.2%), with the majority being gram-negative bacteria (18 samples, 75%). identification index scores showed variation depending on isolate age and sample type. among gram-negative isolates, four samples had red (unidentified) scores, eight had yellow (genus-level), and six had green (species-level) scores. for gram-positive isolates, one sample showed a yellow score, while the rest achieved green scores. these findings emphasize the importance of standardized sample preparation and optimal testing conditions to ensure accurate bacterial identification using maldi tof technology.