The value of MALDI-TOF failure to provide an identification of Staphylococcal species direct from blood cultures and rule out Staphylococcus aureus bacteraemia: a post-hoc analysis of the RAPIDO trial

Abstract

Introduction. Rapid differentiation between Staphylococcus aureus (SA) and coagulase-negative staphylococci (CoNS) is critical in clinical infection. Direct matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) identification from blood culture is highly accurate, but is associated with a significant failure rate, delaying identification. However, MALDI-TOF failure may itself be indicative of CoNS infection. Aim. We sought to examine whether failure of MALDI-TOF direct ID was indicative of CoNS infection and could be used as a diagnostic tool to promote antimicrobial stewardship. Methodology. Results of Gram stains, MALDI-TOF identification and formal identification were extracted from the large, multi-centre RAPIDO trial. All blood cultures with presumed staphylococci were included. MALDI-TOF performance (correct identification, incorrect identification, failed identification) was calculated for each sample and across sites. Risk of SA disease was calculated for each group (correct, incorrect, failed) and across sites. Logistic regression was used to identify if clinical features are associated with MALDI-TOF performance. Results. In the RAPIDO trial, 4312 patients were allocated to the MALDI-TOF arm. After exclusions, 880 patients were eligible and had a blood culture with a Gram stain consistent with presumed staphylococci. In total, 204 of these (23.2 %) were ultimately identified as SA. MALDI-ID was successful 83.9 % of the time, and was 100 % accurate when successful. Failure was more common in CoNS isolates (124/641, 19.3 %) than in SA (13/191, 6.4 %). When MALDI-TOF failed, the risk of SA disease was 9.2 % across the whole cohort, although failure rates and risk of SA disease varied significantly between centres. MALDI-TOF failure was independent of clinical characteristics. Conclusion. Presumed staphylococci that fail direct MALDI-TOF identification from blood culture are significantly more likely to be CoNS isolates than SA. In low-risk or low-prevalence settings, SA therapy can be withheld if MALDI-TOF is unsuccessful.

The Role of Coagulase-Negative Staphylococci Biofilms on Late-Onset Sepsis: Current Challenges and Emerging Diagnostics and Therapies

“…However, although this is true for high-income countries, it is difficult to implement in developing countries. Moreover, for now, it seems that MALDI-TOF has higher sensitivity to detect Gram-negative bacteria from culture bottles, particularly Enterobacteriaceae, than Gram-positive bacteria [ 242 , 243 ]. As such, improvements are still necessary to accurately detect LOS caused by CoNS and to fully implement this methodology in clinical laboratories.…”

Study on the clinical application of Streptococcus pneumoniae serotype detection based on MALDI-TOF MS technology

“…The protein fingerprint of microorganisms is obtained through MALDI-TOF MS technology, which is further compared with the protein fingerprints of known microorganisms. So as to complete the identification and typing of bacteria (Hamilton et al, 2021). MALDI-TOF MS technology has the advantages of automation, rapidity and high throughput (Jang et al, 2021).…”