Rapid direct identification of positive paediatric blood cultures by MALDI-TOF MS technology and its clinical impact in the paediatric hospital setting

Abstract

Objective: Rapid diagnostic tools are imperative for timely clinical decision making, particularly in bacteraemic patients. This study evaluated the performance of a fast, inexpensive novel in house method for processing positive blood cultures for immediate identification of microorganisms by matrix-assisted laser desorption ionization-time of flight mass spectrometry (Vitek MS bioMérieux). We prospectively analyzed the clinical impact of such method on the management of pediatric patients. Result: In total, 360 positive blood cultures were included. Among 318 mono-microbial cultures, in-house method achieved correct identification in 270 (85%) cultures to the species level, whilst 43 (13.5%) gave no identification, and 7 (2.2%) gave discordant identifications. Identification of Gram-negative organisms was accurate to both species and genus level in 99% of isolates, and for Gram positives accuracy was 84% to genus and 81% to species level overall, with accuracy of 100% for Staphylococcus aureus and Enterococcus to the species level. Assessment of the potential impact of direct identification in sixty sequential cases revealed a clear clinical benefit in 35.5% of cases. Benefits included timely antibiotic rationalization, change of medical intervention, and early confirmation of contamination. This study demonstrates a highly accurate in-house method with considerable potential clinical benefits for paediatric care.

A streamlined method for the fast and cost-effective detection of bacterial pathogens from positive blood cultures for the BacT/ALERT blood culture system using the Vitek MS mass spectrometer

“…In line with previous studies using a similar approach [ 16 , 24 – 30 ] it showed in particular excellent performance for gram-negative bacteria, in particular Enterobacterales , P . aeruginos and S .…”

“…Previous studies using the combination of BacT/Alert ® BC bottles and the Vitek ® MS mass spectrometer consistently reported a higher rate of correct identifications for gram-negative bacteria (average 90.4%, 95%-CI = [76.5%, 98.5%]) than for gram-positive bacteria (74.9%, 95%-CI = [53.2%, 95.0%]) [ 16 , 24 – 30 ]. The thicker peptidoglycan layer of the gram-positive cell wall renders these bacteria more resistant to cleavage.…”

“…During the course of this study two similar lysis-centrifugation protocols for the combination of BacT/Alert ® BCs with the Vitek ® MS of were published that showed overall identification rates of 83.9% (95%-CI = [80.6%, 86.9%]) [ 29 ] and 84.9% (95%-CI = [80.5%, 88.7%]) [ 30 ], respectively. They differ from the presented method mainly in the use of different detergents used for protein extraction (Triton (30) and saponin (29) respectively, instead of SDS), indicating that optimization of the extraction chemistry is likely to further improve the performance of rapid identification methods.…”

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

“…Limitations of our study include the small number of carbapenem-resistant bacteria available to perform the broth microdilution technique and the lack of an evaluation of the impact of this technique on patient recovery. However, other studies in this context 14 , 26 have shown that our protocol is very promising in that regard.…”

“…Our study was conducted over a long period of time and included many samples from patients in routine care. We replaced the use of chemical reagents, common to most techniques, 10 , 13 , 14 , 15 with saline, a solution available in any microbiology laboratory that does not harm the environment or laboratory personnel. The technique was inexpensive, easy to perform, and identification results could be obtained within 15 minutes after positive labeling of the blood culture.…”