In Focus: Rapid AST for gram-negative bacteria – case study
Advancing rapid AST for gram-negative bacteria
The emergence of antimicrobial resistance (AMR) proposes a challenge for empirical antibiotic therapy and shows the need for faster diagnostics to guide treatments. The request for rapid antibiotic susceptibility testing of gram-negative bacilli is especially needed in cases of sepsis. Notably, an overall mortality rate of 11 % has been reported, with inadequate treatment being a significant risk factor. When multidrug-resistant microorganisms cause sepsis, mortality rates can reach up to 50 %. In addition to death and disability, AMR has significant economic costs. The World Bank estimates that AMR could result in US$ 1 trillion in additional healthcare costs by 2050. Therefore, rapid confirmation or adjustment of antibiotic treatment could contribute to a reduction in healthcare costs. This is why innovation in new antibiotic susceptibility testing (AST) is vital to address these concerns.
This In Focus paper summarises the highlights from an observational study and explores how the QuickMIC® system could contribute to more efficient sepsis patient management.
Study design & key results
This observational rapid AST study was designed to evaluate the performance of the QuickMIC system (Gradientech, Uppsala, Sweden) in clinical practice at the Dr. Balmis University General Hospital (Alicante, Spain) in a setting with a high incidence of multidrug-resistant bacteria.
The study analysed samples from 86 positive blood cultures of monomicrobial bacteremia caused by Gram-negative bacilli, focusing on species validated for the QuickMIC system. The performance of the QuickMIC system was evaluated against the routine AST method.
Out of the 816 drug-bug combinations tested, eight discrepancies were found, which resulted in a concordance rate of 99.02%. The turnaround time was significantly reduced from 41-48 hours (routine AST) to 4-6 hours using the QuickMIC system. The study revealed that QuickMIC® efficiently determines the effect of 12 antibiotics against the primary gram-negative
bacilli associated with bacteremia, offering critical information for the timely adjustment for escalation or de-escalation of antibiotic therapy.
“Given the existing limitations of currently available rapid AST methods, the clinical utility of QuickMIC® is particularly relevant in the management of P. aeruginosa infections and AmpC-producing Enterobacterales. The use of such rapid methods can help diversify antibiotic use and reduce carbapenem consumption.”