Investigation of direct bacterial identification from positive blood culture bottles by mass spectrometry method

Introduction and aim: Rapid and accurate detection of the causative microorganism in bloodstream infections is of vital importance as it will allow early initiation of treatment. In this study, it was aimed to investigate the direct bacterial identification after various preliminary preparations were made from positive blood culture bottles with mass spectrometry method. Materials and Methods: In this study, 40 pre-prepared spike samples were taken into 5 ml blood gel tubes after giving a positive signal. The sample pellets, which were passed through the centrifugation stage at various times and speeds, were inoculated into the wells in the MALDI-TOF MS slides with the help of a thin wooden rod and waited to dry. After drying, 1 μl of matrix was added to them. After this mixture was dried, the slides were loaded into the device and the identification results were evaluated. Results: Rapid identification results were consistent with the identification from the bakterial colonies with the following ratios: E. coli 80%, K. pneumoniae 100%, A. baumannii 66%, E. cloacae 50%, S. aureus 66%, S. epidermidis 66%, S. hominis 50%, S. haemolyticus 25%, E. faecalis 100%. In line with these results, 80% compatible results were seen in gram-negative bacteria; 45% consistent results were found in gram-positive bacteria Conclusion: As a result of direct identification from positive blood cultures with MALDI-TOF MS, 80% success was achieved in gram-negative bacteria, while this rate was 45% in gram-positive bacteria despite different methods being tried. In this regard, large and comprehensive studies are needed, especially for gram-positive bacteria. Keywords: sepsis, blood culture, direct identification, MALDI-TOF MS