An enzymatic radioassay for gentamicin

Area of Science:

• Biochemistry
• Analytical Chemistry
• Pharmacology

Background:

• Gentamicin is a crucial antibiotic for treating severe bacterial infections.
• Accurate therapeutic drug monitoring of gentamicin is essential to optimize efficacy and minimize toxicity.
• Existing assay methods may have limitations in sensitivity, specificity, or turnaround time.

Purpose of the Study:

• To develop and evaluate a novel enzymatic, radiochemical assay for quantifying serum gentamicin.
• To assess the assay's sensitivity, linearity, and specificity.
• To compare the new method with established radioimmunoassay and microbiological techniques.

Main Methods:

• Utilized gentamicin 3-acetyl-transferase and [acetyl-14C]acetyl-Coenzyme A for enzymatic labeling.
• Incubated samples at 37°C for 10 minutes for stoichiometric transfer of the radioactive label.
• Absorbed labeled gentamicin onto phosphocellulose paper discs for separation and subsequent liquid scintillation counting.

Main Results:

• The assay demonstrated high sensitivity, detecting gentamicin concentrations as low as 0.2 mg/liter.
• A linear response was observed for gentamicin concentrations ranging from 0.2 to 20 mg/liter.
• The method showed specificity for gentamicin, with minimal reactivity to structural analogs like sisomicin and slight reactivity to tobramycin and netilmicin; no other interferents were identified.

Conclusions:

• The described enzymatic, radiochemical assay provides a sensitive, specific, and quantitative method for measuring serum gentamicin.
• This assay offers a reliable alternative for therapeutic drug monitoring of gentamicin.
• Further comparison with radioimmunoassay and microbiological methods indicates its potential clinical utility.