Evaluation of an optimized method to directly identify bacteria from positive blood cultures using MALDI‐TOF mass spectrometry

Abstract

Background: Although various methods have been developed to directly identify bacteria from positive blood cultures by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS), the necessity of using commercial kits still leads to a high cost and long assay time. Moreover, few evaluations of these methods have been conducted. This study aimed to evaluate the feasibility of an optimized MALDI-TOF MS method for direct identification of bacteria in positive blood cultures. Methods: A total of 829 non-repeated positive cultures were collected from July 2018 to August 2019, and direct identification was performed by an optimized MALDI-TOF MS method. The same positive blood cultures were sub-cultivated to obtain a single bacterial colony and identified by classical biochemical BD testing, which is the gold standard to compare the accuracy of direct identification of positive blood cultures by MALDI-TOF MS.Results: After excluding 7 false-positive samples from the 829 positive blood cultures, the most accurate rate of direct identification by this optimized MALDI-TOF MS method was for gram-negative bacteria (91.5%), followed by gram-positive bacteria (88.3%), fungi (84.8%), anaerobic bacteria (80%), and other rare bacteria (66.67%). Conclusion:Common bacteria in positive blood cultures can be identified directly within 1 hour by MALDI-TOF MS, and thus, this optimized method can be used as a primary identification method by clinicians. Routine implementation of this method may significantly increase the optimal utilization rate of antibiotics and decrease mortality in bacteremia patients. K E Y W O R D S bacteria, blood culture, identification, MALDI-TOF MS S U PP O RTI N G I N FO R M ATI O N Additional supporting information may be found online in the Supporting Information section.Evaluation of an optimized method to directly identify bacteria from positive blood cultures using MALDI-TOF mass spectrometry. J Clin Lab Anal. 2020;34:e23119. https ://doi.

Evaluation of Rapid Sepsityper® protocol and specific MBT-Sepsityper module (Bruker Daltonics) for the rapid diagnosis of bacteremia and fungemia by MALDI-TOF-MS

“…The majority of direct identification protocols are "in-house" protocols using variable extraction steps and lysis reagents ( Table 1). Centrifugation alone with no lysis reagent has shown sensibilities ranging from 43 to 95% between studies and can be performed using a separator tube [41,42,[48][49][50][51][52]. Different lysis reagents may be employed, in particular Saponin, Sodium dodecyl sulfate (SDS), Ammonium chloride or Triton X-100 with sensibilities ranging from 53 to 86% [34,53,54].…”

“…In particular, despite their low cost, the important handson-time of MALDI-TOF-MS assays still prevents many laboratories to perform rapid identification on positive blood cultures, which results in a loss of opportunity for the patients. In-house and commercial protocols such as the Sepsityper ® kit (Bruker Daltonics GmbH, Bremen, Germany) usually take between 20 to 40 min of turnaround time [22,28,[30][31][32][33][34][35][36][37][38][39][40][41][42][43]. A comprehensive overview of current performances and estimated hands-on time of the different rapid identification methods using MALDI-TOF-MS on positive blood cultures has been gathered in Table 1.…”

Rapid bacterial identification by MALDI-TOF MS directly from blood cultures and rapid susceptibility testing: A simple approach to reduce the turnaround time of blood cultures

“…The technique was inexpensive, easy to perform, and identification results could be obtained within 15 minutes after positive labeling of the blood culture. It is important to highlight that our study was performed using a MALDI TOF VITEK® MS from bioMérieux, in contrast to most published studies performed using Bruker Daltonics' MALDI TOF MS. 10 , 13 , 16 , 17 MALDI-TOF MS is an efficient and cost-effective method for bacterial identification compared to routine biochemical panels. 18 Its use in rapid identification of pathogens causing sepsis is essential to provide clinicians with information to decide on appropriate therapy.…”

Trigging Isothermal Circular Amplification-Based Tuning of Rigorous Fluorescence Quenching into Complete Restoration on a Multivalent Aptamer Probe Enables Ultrasensitive Detection of Salmonella

“…To date, many methods for detecting bacterial pathogens have been developed to ensure food safety for human health. − The most commonly used detection technique is the legislated culture method based on plate counting, which suffers in particular from long turnaround times of usual 5 days to sampling, pre-enrichment on common media, and selective enrichment on specific media . In clinical settings, this long turnaround time for pathogen identification might exceed the treatment window for seriously ill patients and the lack of information on the causative pathogen might cause the use of inappropriate antibiotic drugs.…”

“…10−12 The most commonly used detection technique is the legislated culture method based on plate counting, which suffers in particular from long turnaround times of usual 5 days to sampling, pre-enrichment on common media, and selective enrichment on specific media. 13 In clinical settings, this long turnaround time for pathogen identification might exceed the treatment window for seriously ill patients and the lack of information on the causative pathogen might cause the use of inappropriate antibiotic drugs. As a substitute for the standard method, molecular amplification methods (e.g., polymerization chain reaction, PCR) and immunologically based methods (e.g., enzyme-linked immunosorbent assay, ELISA) have opened up myriad new possibilities for pathogen detection and have already made impressive achievements.…”