A fluorogenic biotracer for reliable detection of staphylococcal beta-lactamase: towards improved precision therapy in severe MSSA infections.

Authors

Céline Dupieux, Patricia Martins Simoes, Benjamin Youenou, François Vandenesch, Anne Tristan, Frédéric Laurent

Published in

The Journal of antimicrobial chemotherapy. Volume 81. Issue 9. Aug 04, 2026.

Abstract

Accurate detection of staphylococcal beta-lactamase remains a diagnostic challenge, despite its importance for guiding antibiotic therapy, particularly in severe infections, such as endocarditis and bacteraemia. Currently, no available method reliably detects beta-lactamase activity in all staphylococcal species. Here, we evaluated a novel fluorogenic biotracer, 352600-C (MOLSID, Lyon, France), designed to detect beta-lactamase activity in staphylococci.
The 352600-C biotracer was incorporated into Mueller-Hinton agar plates onto which staphylococcal strains were subcultured at 37°C. Colony fluorescence was assessed at 4, 6 and 24 h using a 365 nm UV lamp. The assay was performed on a large collection of blaZ-positive (n = 124, including BlaZ types A, B, C and D) and blaZ-negative (n = 69) staphylococci from 18 species (Staphylococcus aureus, n = 100; S. non-aureus, n = 93). Molecular detection of the blaZ gene using WGS served as the gold standard. Phenotypic susceptibility to penicillins was also tested using EUCAST recommendations.
After 4, 6 and 24 h of incubation, the assay showed sensitivities of 92.2%, 96.9% and 100% for S. aureus and 50.0%, 88.3% and 100% for non-aureus staphylococci, respectively. None of the 69 blaZ-negative strains produced fluorescent colonies (specificity 100%). Notably, the assay detected all BlaZ types. Penicillin disc diffusion showed 98.4% sensitivity and 77.8% specificity for MSSA.
This novel assay for the detection of staphylococcal beta-lactamase demonstrated simplicity, rapidity and excellent accuracy after 24 h incubation (100% sensitivity and specificity) across a genetically diverse and representative collection of clinical isolates, making it a valuable tool for routine diagnostics and antimicrobial stewardship.

PMID:
42599769
Bibliographic data and abstract were imported from PubMed on 15 Aug 2026.

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