European Study Finds Time Kill Curve Testing for Antibiotics Lacks Standardization Across Labs
A six-centre European study 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 global antimicrobial research infrastructure at a time when antibiotic resistance is a major public health concern.
Researchers from six European laboratories participating in the GNA NOW consortium tested the antibiotic meropenem against three strains of E. coli to assess how reproducible time kill curve (TKC) experiments are both within and between testing centres. TKCs are a critical tool for understanding how antibiotics kill bacteria over time, yet no formal international standardisation exists for how they should be conducted. The study found that within each centre, same-day and different-day replications were generally consistent, with statistical tests yielding p-values above 0.05. However, inter-centre comparisons produced p-values below 0.05, indicating meaningful variation in measured bacterial load across sites. Investigators documented numerous methodological differences between centres, including how bacterial inocula were prepared, meropenem concentrations were made up, vessel materials and volumes used, and whether cultures were agitated or kept static. To control for variables, the same meropenem stock, growth media, and bacterial strains were shipped from a central laboratory to all participating sites. The authors conclude that formal standardisation of TKC methodology is urgently needed to ensure that antimicrobial pharmacodynamic data is comparable across research institutions.
What's missing
The study does not address whether the observed inter-centre variability was large enough to alter clinical or regulatory conclusions about antibiotic efficacy, nor does it propose or evaluate specific standardisation protocols. It is also limited to one antibiotic (meropenem) and one bacterial species (E. coli), so generalisability to other drug-pathogen combinations remains untested. As a preprint, these findings have not yet undergone formal peer review.
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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