Comparison of Mass Spectrometry Method Directly from Positive Blood Culture Medium and Conventional Microbiological Method in the Identification of Microorganisms

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Laboratorinė medicina. 2019,
t. 21,
Nr. 1,
p. 13 -
19

Aim. To evaluate the results of the identification of microorganisms directly from positive blood culture medium by mass spectrometry and conventional microbiological method.
Methods and the study subjects. Study involved only positive blood cultures. Identification of microorganisms by conventional microbiological method was compared with identification of microorganisms directly from positive blood culture medium by the MALDI-TOF mass spectrometry. For direct identification of microorganisms, the method of extraction with formic acid was used. Statistical analysis was performed using SPSS 2.0 software package, the results were considered statistically significant when P value was less than 0.05.
Results. 102 positive blood cultures were tested. 10.8% of positive blood cultures were polymicrobial, 89.2% - monomicrobial. The study found that in 89.2% cases, the results between two methods coincided, but in 10.8% cases the results did not coincide. It was observed that this incompatibility was caused by cases of polymicrobial bacteremia.
Identifying microorganisms by conventional microbiological method, one or more infection agents can be detected and only one agent is detected by direct identification from positive blood culture. However, using this direct method, the time of identification of microorganisms was shortened to less than 4 h after the BACTECTM FX positive signal was detected.
Conclusions. The identification of microorganisms directly from positive blood culture samples by mass spectrometry takes less time, but some of the pathogens are not identified in the presence of a polymicrobial infection, so this method cannot currently replace the conventional microbiological method.

 

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