Direct identification of bacteria from positive blood culture bottles by VITEK-MS: evaluation of two lysis-centrifugation methods
DOI:
https://doi.org/10.61529/idjp.v35i3.482Abstract
Background: Bloodstream infections cause significant global morbidity and mortality, and although MALDI-TOF MS accelerates pathogen identification, it still requires subculture. This study evaluated two in-house lysis-centrifugation methods (LCMs) using sodium dodecyl sulfate (SDS) and Triton X-100 for direct pathogen identification from positive blood culture bottles. To compare the diagnostic accuracy of SDS- and Triton X-100-based LCMs for direct bacterial identification from positive blood culture bottles using VITEK MS.
Material and Method: This study was conducted at the Chughtai Institute of Pathology, Lahore. Positive blood culture bottles were analyzed using the standard culture-based method and both LCM protocols in parallel. Blood cultures with polymicrobial growth, yeast on Gram stain, or no identification by the standard-of-care method were excluded. Concordance, diagnostic accuracy, and processing time were assessed.
Results: A total of 251 monobacterial positive blood cultures were analyzed. The SDS and Triton X-100 protocols correctly identified 62.5% and 59.8% of isolates, respectively (p = 0.52). Concordance was higher for Enterobacterales (66.7%) than for non-Enterobacterales (50.0% and 32.1%, respectively). Identification rates for Salmonella enterica were significantly lower than for other Enterobacterales (p < 0.001). Both methods required less than 15 minutes of hands-on time per sample and showed fair agreement (κ ≈ 0.31).
Conclusion: Both LCMs provided rapid, low-cost identification with comparable performance. Their utility was greater for Enterobacterales other than S. enterica, while low S. enterica identification rates limit their application for rapid enteric fever diagnosis.
Key words: Blood culture, MALDI-TOF, Sepsis, Bloodstream infection, Lysis centrifugation.
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