Akademik Veri Yönetim Sistemi
Diagnostic Microbiology and Infectious Disease, cilt.115, sa.4, 2026 (SCI-Expanded, Scopus)
Objective: Two-dimensional (2D) checkerboard assays are used for dual antimicrobial combinations; however, adding a third agent increases the concentration space to three dimensions, complicating plate layout and reporting. This study present a methodological framework for implementing three-dimensional (3D) checkerboard designs and reporting interaction outcomes using the fractional inhibitory concentration index (FICI). Methods: In the 3D design, ceftriaxone (CRO) was fixed on separate plates at six different concentrations. Cinnamaldehyde (CIN) and carvacrol (CAR) were diluted on each plate in a 2D checkerboard format. This generated 54 unique CINCAR pairs per plate and 324 triple combinations across six plates. For each CRO plate, the inhibition boundary was determined by systematic row and column-wise scanning. As ΣFICI thresholds are not fully standardized, outcomes were additionally interpreted using three classification criteria. The demonstration dataset was generated using Klebsiella pneumoniae ATCC 10031. Results: In 2D plates, median and minimum ΣFICI values varied across pairs. In the 3D design, no inhibition boundary was identifiable at CRO 8 and 4 µg/mL because all wells were fully inhibited. Therefore, reporting was based on CRO plates where an inhibition boundary could be defined (2-0.25 µg/mL). Parallel classification showed that categorical interpretations varied with the ΣFICI thresholds. Conclusion: This framework enables the practical 3D checkerboard setup and transparent reporting using inhibition boundary-based median and minimum ΣFICI summaries. However, this should not be considered a direct clinical inference but a methodological reporting approach. Future studies should validate it across multiple clinical isolates and selected combinations, ideally alongside complementary synergy methods.