Developing a Simple, Applicable, and Reliable Method to Produce and Standardize an Epsilometer (Etest) Strip for Antimicrobial Susceptibility and Minimum Inhibitory Concentration Evaluations

Document Type : Original Article

Authors

Department of Pharmaceutical Quality Control, School of Pharmacy, Shiraz University of Medical Sciences, Shiraz, Iran

10.30476/tips.2026.110209.1346

Abstract

Microbial infections remain a major global health burden due to rising antimicrobial resistance. Rapid and accurate determination of minimum inhibitory concentration (MIC) is essential. Conventional methods like broth microdilution are limited by long turnaround times or poor precision. The Etest Epsilometer strips (Etest) provides accurate MIC readings within 16-24 hours but are imported in many countries, including Iran, facing high costs and supply issues. This study developed a simple, cost-effective method to produce Etest-like strips domestically for water-soluble antibiotics using cellulose-based substrates (K2) and a locally available adhesive (G1). Ciprofloxacin and Escherichia coli were used as models. Drug loading and release were quantified by validated UV-Vis spectrophotometry (λmax=270 nm, R²=0.9998, accuracy 97.21%, precision <3%). Prototype strips showed stable release after 20 minutes. Raw MIC readings from the prepared strip were calibrated against CLSI reference methods. Strips remained stable for at least two months at room temperature (25±2 °C) and 2-8 °C. This locally producible platform enables import substitution, accelerates susceptibility testing, and strengthens antimicrobial stewardship in resource-limited settings.

Highlights

Hashem Montaseri (Google Scholar)

Zahra Sobhani (Google Scholar)

Keywords

References

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Trends in Pharmaceutical Sciences and Technologies
Volume 11, Issue 4 - Serial Number 44
December 2025
Pages 357-372

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