Direct identification of bacteria from positive blood culture bottles by using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry - a systematic review and meta-analysis

Introduction

We perform a systematic review and meta-analysis of direct identification protocols of bacterial pathogens from patients with bloodstream infections (BSI) using matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry (MALDI-TOF).

Goals

To evaluate protocols in operation for pathogen detection directly from positive blood culture bottles.

Methods

The study was registered at PROSPERO (2022CRD42022293236). Screening and study selection followed recommendation by PRISMA. We defined correct identification rate as CIR(X) = . Meta-analysis was performed using the 'dmetar', 'meta' and 'metafor' packages of the R software. Fixed and random-effects models were used to estimate the pooled CIR of different bacterial groups and species. Upon detection of significant heterogeneity, the random-effects model was considered and influence as well outlier analysis were performed.

Results

We screened 1296 titles, 211 abstracts and 167 full texts. A total of 145 datasets from 93 studies were included. There was a significant heterogeneity in the data sets (I² = 99.2%). The most frequent blood culture systems, mass spectrometry manufacturer, separation method and protein extraction method were BD BACTECTM (94/145, 64.8%), Bruker (117/145, 80.7%), centrifugation (119/145; 82.1%), and in-house-protocol including saponin (59/145; 40.1%). The most frequent commercial extraction protocol was the Sepsityper (37/145, 25.6%). Total CIR, CIR of gram-positive bacteria and gram-negative bacteria was 0.72 (95% CI: 0.69-0.75), 0.62 (95% CI: 0.58-0.66) and 0.85 (95% CI: 0.83-0.88), respectively. CIR of Staphylococcus aureus, Streptococcus pneumoniae, Enterobacterales and Pseudomonas spp. was 0.78 (95% CI: 0.73-0.83), 0.36 (95% CI: 0.29-0.43), 0.90 (95% CI: 0.87-0.92) and 0.86 (95% CI: 0.81-0.9). Significant differences within bacterial groups and detection methods were detected.

Summary

Direct identification protocols can detect a high rate of pathogens of BSI. However, the observed overall CIR suggests that protocols need further improvement to replace the current standard of care.