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. 2024 Jul 26;14(15):1611.
doi: 10.3390/diagnostics14151611.

Comparison of the Direct Identification and Short-Term Incubation Methods for Positive Blood Cultures via MALDI-TOF Mass Spectrometry

Shu-Fang Kuo  1   2 , Tsung-Yu Huang  3   4   5 , Chih-Yi Lee  1   2 , Chen-Hsiang Lee  3   4   6
Affiliations

Comparison of the Direct Identification and Short-Term Incubation Methods for Positive Blood Cultures via MALDI-TOF Mass Spectrometry

Shu-Fang Kuo et al. Diagnostics (Basel). .

Abstract

Timely pathogen identification in bloodstream infections is crucial for patient care. A comparison is made between positive blood culture (BC) pellets from serum separator tubes using a direct identification (DI) method and colonies on agar plates from a short-term incubation (STI) method with a matrix-assisted laser desorption/ionization Biotyper for the evaluation of 354 monomicrobial BCs. Both the DI and STI methods exhibited similar identification rates for different types of bacteria, except for Gram-positive and anaerobic bacteria. The DI method's results aligned closely with the STI method's results for Enterobacterales, glucose-non-fermenting Gram-negative bacilli (GNB), and carbapenem-resistant Enterobacterales. The DI method exhibited high concordance with the conventional method for GNB identification, achieving 88.2 and 87.5% accuracy at the genus and species levels, respectively. Compared with the STI method, the DI method showed a less successful performance for Gram-positive bacterial identification (50.5 vs. 71.3%; p < 0.01). The DI method was useful for anaerobic bacterial identification of slow-growing microorganisms without any need for colony growth, unlike in the STI method (46.7 vs. 13.3%; p = 0.04). However, both methods could not identify yeast in positive BCs. Overall, the DI method provided reliable results for GNB identification, offering many advantages over the STI method by significantly reducing the turnaround time and enabling quicker pathogen identification in positive BCs.

Keywords: antibiotics; antimicrobial stewardship program; bloodstream infections; rapid identification; sepsis.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

Figure 1
Figure 1
Flow chart of the short-term incubation (STI) method and the direct identification (DI) method.
Figure 2
Figure 2
Direct identification (DI) method results from positive blood cultures. GNB, Gram-negative bacteria; GPB, Gram-positive bacteria. * No peak in MALDI-TOF MS analysis of the DI method.
Figure 3
Figure 3
Comparison of identification rate between the direct identification (DI) and short-term incubation (STI) methods. CRE, carbapenem resistant Enterobacterales; GNB, Gram-negative bacteria; GPB, Gram-positive bacteria; GPC, Gram-positive cocci; n, tested number. * p < 0.05 indicates significant difference.
See this image and copyright information in PMC

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