Rapid microbiologic assay of tobramycin

Area of Science:

• Microbiology
• Clinical Chemistry
• Pharmacology

Background:

• Accurate measurement of antibiotic levels in serum is crucial for effective treatment.
• Traditional overnight assays for tobramycin can be time-consuming.
• Development of rapid diagnostic methods is needed for timely therapeutic adjustments.

Purpose of the Study:

• To compare the accuracy and reproducibility of different rapid plate diffusion assays for tobramycin in serum.
• To evaluate the impact of incubation time and temperature on assay performance.
• To identify an optimal rapid assay for tobramycin quantitation.

Main Methods:

• Comparison of multiple rapid plate diffusion assays against a standard overnight assay.
• Use of Klebsiella edwardsii var. atlantae as the test microorganism.
• Evaluation of different inoculum dilutions (1:50-1:100 and 1:10) and incubation conditions (5 hours at 35°C, 2.5 hours at 35°C, and 2.5 hours at 40°C).

Main Results:

• A 5-hour assay with a 1:50-1:100 dilution at 35°C demonstrated comparable reproducibility and accuracy to the overnight assay.
• A 2.5-hour assay at 35°C was found to be inaccurate.
• Increasing incubation temperature to 40°C accelerated bacterial growth and improved zone of inhibition clarity.
• The 2.5-hour assay at 40°C proved to be as accurate and reproducible as the 5-hour and overnight assays.

Conclusions:

• Rapid tobramycin serum assays are feasible and can provide reliable results.
• Optimizing incubation temperature to 40°C significantly enhances the performance of short-incubation assays.
• A 2.5-hour plate diffusion assay at 40°C offers a rapid, accurate, and reproducible alternative to traditional overnight methods for tobramycin quantitation.