European Study Finds Time Kill Curve Testing for Antibiotics Lacks Standardization Across Labs
A six-centre European collaboration found that time kill curve (TKC) assessments — a standard method for evaluating antibiotic effectiveness — produced inconsistent results between laboratories, even when using the same bacterial strains and drug. While results were reproducible within individual centres, significant variation emerged when comparing across sites. The findings highlight a gap in antimicrobial research infrastructure that could affect the reliability of drug development data.
Researchers from six European centres participating in the GNA NOW consortium conducted a coordinated study testing meropenem against three strains of E. coli to evaluate how reproducible time kill curve (TKC) assessments are both within and between laboratories. TKCs are a critical tool for characterising how antibiotics kill bacteria over time, yet no formal standardisation exists for the methodology. The study found that within each centre, same-day and different-day replications were generally consistent (p>0.05), suggesting individual labs can reliably reproduce their own results. However, inter-centre comparisons showed statistically significant differences (p<0.05) in total bacterial load measurements, indicating that the same experiment conducted at different sites yields different outcomes. Investigators documented numerous methodological differences between centres, including variations in inoculum preparation, meropenem handling, vessel volume and materials, and whether cultures were agitated or static. The authors conclude that without standardisation, TKC data generated across different research centres may not be directly comparable, potentially undermining multi-site antimicrobial studies and drug development pipelines.
What's missing
The study does not report whether the observed inter-centre variability was large enough to change clinical or pharmacodynamic conclusions (e.g., whether a drug would be classified as bactericidal vs. bacteriostatic), which would help quantify the real-world impact of the inconsistency. It also does not propose a specific standardised protocol, leaving open the question of which methodological variables are most critical to harmonise.
What different sources said
- bioRxivCenter
Is there a need to implement standardisation into in vitro antimicrobial evaluation systems? A European collaboration perspective
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